Hi 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA 


GIFT  OF 


Jj^nr\A^M^ 

04  |  qo  ,,,  ^T, 

C/^5S  J 


gale  'Bicentennial  publication!? 

CONTRIBUTIONS  TO  MINERALOGY 
AND  PETROGRAPHY 


pale  'Bicentennial  publications 

With  the  approval  of  the  President  and  Fellows 
of  Yale  University,  a  series  of  volumes  has  been 
prepared  by  a  number  of  the  Professors  and  In- 
structors, to  be  issued  in  connection  with  the 
Bicentennial  Anniversary,  as  a  partial  indica- 
tion of  the  character  of  the  studies  in  which  the 
University  teachers  are  engaged. 

This   series   of  volumes   is    respectfully  dedicated  to 

d5raOuate$  of  tiie 


CONTRIBUTIONS 

TO 

MINERALOGY    AND 
PETROGRAPHY 

FROM   THE    LABORATORIES    OF   THE 

SHEFFIELD    SCIENTIFIC    SCHOOL 

OF 

YALE    UNIVERSITY 

EDITED    BY 

S.    L.    PENFIELD 

\\ 

Professor  of  Mineralogy 
AND 

L.  V.  PIRSSON 

Professor  of  Physical  Geology 


NEW   YORK:   CHARLES   SCRIBNER'S   SONS 

LONDON:    EDWARD   ARNOLD 

1901 


Copyright,  1901, 
BY  YALE   UNIVERSITY 


Published,  August, 


UNIVERSITY   PRESS    •    JOHN    WILSON 
AND   SON    •     CAMBRIDGE,    U.S.A. 


PREFACE 

THIS  volume  comprises  a  series  of  reprints  of  some  of  the 
most  important  of  the  papers  containing  the  results  of  the  re- 
searches made  in  the  Chemical,  Mineralogical,  and  Petrographical 
laboratories  at  Yale  in  the  lines  of  Mineralogy  and  Petrography. 
It  is  believed  that,  gathered  from  various  scattered  sources  and 
put  into  this  compact  and  permanent  form,  they  will  prove  a 
useful  addition  to  the  literature  of  these  closely-allied  sciences. 
It  is  thought,  also,  that  the  historical  accounts  of  the  develop- 
ment of  these  sciences  in  Yale  University  will  prove  of  interest, 
and  the  appended  bibliographies  will  indicate  the  scope  and 
character  of  the  work  which  has  been  undertaken  and  the  re- 
sults which  have  been  attained.  The  mineralogical  portion  of 
the  volume  has  been  written  or  edited  by  S.  L.  PENFIELD  ;  the 
petrographical  part,  by  L.  V.  PIRSSON. 

YALE  UNIVERSITY,  NEW  HAVEN, 
May,  1901. 


04 1 9' 


CONTENTS. 

PART  I.— MINERALOGY. 

EDITED  BY  S.  L.  PENFIELD. 

PAGE 
HISTORY  OF   THE   MINERALOGICAL   DEPARTMENT   AND   OF   THE 

DEVELOPMENT  OF  MINERALOGY  AT  YALE.     By  S.  L.  Pentield        3 

ON  AMERICAN  SPODUMENE.     By  George  J.  Brush 30 

ON   SUSSEXITE,  A  NEW  BORATE   FROM   MINE  HILL,   FRANKLIN 

FURNACE,  SUSSEX  Co.,  NEW  JERSEY.     By  George  J.  Brush  .       33 

ON    HORTONOLITE,  A    NEW  MEMBER  OF    THE    CHRYSOLITE  GROUP. 

By  George  J.  Brush.  WITH  MEASUREMENTS  AND  OBSERVA- 
TIONS ON  THE  CRYSTALLINE  FORM  OF  THE  MINERAL.  By 
John  M.  Blake 37 

ON  GAHNITE    FROM    MINE    HILL,   FRANKLIN    FURNACE,   NEW 

JERSEY.     By  George  J.  Brush 42 

ON  THE  CHEMICAL  COMPOSITION  OF  DURANGITE.    By  George  J. 

Brush 45 

ON  A  NEW  AND  REMARKABLE  MINERAL  LOCALITY  AT  BRANCH- 
VILLE,  IN  FAIRFIELD  COUNTY,  CONNECTICUT  ;  WITH  A  DE- 
SCRIPTION OF  SEVERAL  NEW  SPECIES  OCCURRING  THERE. — 
FIRST  PAPER.  By  George  J.  Brush  and  Edward  S.  Dana  .  .  48 

SECOND  BRANCHVILLE  PAPER.     By  George  J.  Brush  and  Edward 

S.  Dana 72 

THIRD  BRANCHVILLE   PAPER.     By  George  J.  Brush  and  Edward 

S.  Dana 81 

FOURTH  BRANCHVILLE  PAPER.  —  SPODUMENE  AND  THE  RESULTS 

OF  ITS  ALTERATION.     By  George  J.  Brush  and  Edward  S.  Dana      86 

FIFTH  BRANCHVILLE  PAPER.  By  George  J.  Brush  and  Edward 
S.  Dana.  WITH  ANALYSES  OF  SEVERAL  MANGANESIAN 
PHOSPHATES.  By  Horace  L.  Wells 105 


x  CONTENTS. 

PAGE 
ON  THE  CHEMICAL  COMPOSITION  OF  AMBLYGONITE.     By  Samuel 

L.  Penfield 121 

ON  THE   CHEMICAL   COMPOSITION  OF   CHILDRENITE.      By  S.  L. 

Penfield 124 

BASTNASITE  AND  TYSONITE  FROM   COLORADO.    By  O.  D.  Allen 

and  W.  J.  Comstock 126 

CRYSTALLIZED  TIEMANNITE  AND  METACINNABARITE.     By  Samuel 

L.  Penfield 130 

GERHARDTITE   AND   ARTIFICIAL  BASIC   CUPRIC   NITRATES.     By 

H.  L.  Wells  and  S.  L.  Penfield 134 

ON  THE  CHEMICAL  COMPOSITION  OF  HERDERITE.  By  S.  L.  Pen- 
field  and  D.  N.  Harper 138 

ON  THE    CHEMICAL   COMPOSITION   OF   RALSTONITE.       By  S.  L. 

Penfield  and  D.  N.  Harper 143 

SPERRYLITE,  A  NEW  MINERAL.     By  Horace  L.  Wells      .     .     .     .     151 
ON  THE  CRYSTALLINE  FORM  OF  SPERRYLITE.     By  S.  L.  Penfield     157 

RESULTS  OBTAINED  BY  ETCHING  A  SPHERE  AND  CRYSTALS  OF 
QUARTZ  WITH  HYDROFLUORIC  ACID.  By  Otto  Meyer  and 
Samuel  L.  Penfield 160 

ON  SPANGOLITE,  A  NEW  COPPER  MINERAL.     By  S.  L.  Penfield   .     168 
ON  MORDENITE.     By  Louis  V.  Pirsson 176 

ON  THE  COMPOSITION  OF   POLLUCITE  AND  ITS  OCCURRENCE  AT 

HEBRON,  MAINE.     By  H.  L.  Wells 183 

THE  CHEMICAL  COMPOSITION  OF  IOLITE.     By  O.  C.  Farrington  .     193 

ON  ARGYRODITE   AND   ITS    OCCURRENCE   AT  A   NEW  LOCALITY 

IN  BOLIVIA.     By  S.  L.  Penfield 198 

ON  THE  CHEMICAL  COMPOSITION  OF  STAUROLITE,  AND  THE 
REGULAR  ARRANGEMENT  OF  ITS  CARBONACEOUS  INCLU- 
SIONS. By  S.  L.  Penfield  and  J.  H.  Pratt 207 

ON    THE   CHEMICAL    COMPOSITION    OF   CHONDRODITE,   HUMITE, 

AND  CLINOHUMITE.     By  S.  L.  Penfield  and  W.  T.  H.  Howe    .     218 

ON    THE    CHEMICAL     COMPOSITION    AND     RELATED     PHYSICAL 

PROPERTIES  OF  TOPAZ.     By  S.  L.  Penfield  and  J.  C.  Minor,  Jr.     231 


CONTENTS.  xi 

PAGE 
ON   CANFIELDITE,  A  NEW   SULPHOSTANNATE   OF    SILVER,  FROM 

BOLIVIA.     By  S.  L.  Penfield 242 

ON   THE    OCCURRENCE   OF   THAUMASITE    AT   WEST   PATERSON, 

NEW  JERSEY.     By  S.  L.  Penfield  and  J.  H.  Pratt       ....     246 

ON  PEARCEITE,  A  SULPHARSENITE  OF  SILVER.     By  S.  L.  Penfield     252 

ON  NORTHUPITE;  PIRSSOXITE,  A  NEW  MINERAL;  GAY-LUSSITE 
AND  HANKSITE  FROM  BORAX  LAKE,  SAN  BERNARDINO 
COUNTY,  CALIFORNIA.  By  J.  H.  Pratt 261 

ON  WELLSITE,  A  NEW  MINERAL.      By  J.  H.  Pratt  and  H.  W. 

Foote 275 

ON  BIXBYITE,   A   NEW   MINERAL.     By  S.  L.  Penfield  and  H.  W. 

Foote 283 

ON  THE  CHEMICAL  COMPOSITION  OF  HAMLINITE  AND  ITS  OC- 
CURRENCE WITH  BERTRANDITE  AT  OXFORD  COUNTY,  MAINE. 
By  S.  L.  Penfield 287 

ON  CLINOHEDRITE,   A   NEW  MINERAL    FROM   FRANKLIN,   N.  J. 

By  S.  L.  Penfield  and  H.  W.  Foote        291 

ON   THE  CHEMICAL   COMPOSITION   OF    TOURMALINE.     By   S.  L. 

Penfield  and  H.  W.  Foote 297 

SOME  NEW  MINERALS  FROM  THE  ZINC  MINES  AT  FRANKLIN, 
N.  J.,  AND  NOTE  CONCERNING  THE  CHEMICAL  COMPOSITION 
OF  GANOMALITE.  By  S.  L.  Penfield  and  C.  H.  Warren  .  .  325 

ON  THE  CHEMICAL  COMPOSITION  OF  SULPHOHALITE.     By   S.   L. 

Penfield        343 

ON  THE  INTERPRETATION  OF  MINERAL  ANALYSES:  A  CRITICISM 
OF  RECENT  ARTICLES  ON  THE  CONSTITUTION  OF  TOURMA- 
LINE. By  S.  L.  Penfield 348 

ON  SOME  INTERESTING  DEVELOPMENTS   OF   CALCITE  CRYSTALS. 

By  S.  L.  Penfield  and  W.  E.  Ford 357 

ON  THE  CHEMICAL  COMPOSITION  OF  TURQUOIS.  By  S.  L.  Pen- 
field  365 

THE  STEREOGRAPHIC  PROJECTION  AND  ITS  POSSIBILITIES,  FROM 

A  GRAPHICAL  STANDPOINT.    By  S.  L.  Penfield 371 


xii  CONTENTS. 

PART   II.  — PETROGRAPHY. 

EDITED  BY  L.  V.  PIRSSON. 

PAGE 
HISTORY  OF    THE    PETROGRAPHICAL   DEPARTMENT.     By  L.   V. 

Pirsson 381 

ON  THE  COMPOSITION  OF  THE  LABRADORITE  ROCKS  OF  WATER- 

VILLE,  NEW  HAMPSHIRE.     By  E.  S.  Dana 387 

GEORGE  W.  HAWES 391 

ON  A   GROUP  OF  DISSIMILAR   ERUPTIVE  ROCKS  IN    CAMPTON, 

NEW  HAMPSHIRE.     By  George  W.  Hawes 394 

THE   ALBANY    GRANITE,   NEW  HAMPSHIRE,   AND   ITS   CONTACT 

PHENOMENA.     By  George  W.  Hawes 400 

ON  THE   PETROGRAPHY  OF  SQUARE  BUTTE   IN    THE   HIGHWOOD 

MOUNTAINS  OF  MONTANA.     By  L.  V.  Pirsson 415 

PETROGRAPHY  OF  THE  ROCKS  OF  YOGO  PEAK.     By  L.  V.  Pirsson    436 

MISSOURITE,  A  NEW  LKUCITE  ROCK  FROM  THE  HIGHWOOD 
MOUNTAINS  OF  MONTANA.  By  Walter  H.  Weed  and  Louis  V. 
Pirsson 457 

ANDESITES  OF  THE  AROOSTOOK  VOLCANIC  AREA  OF  MAINE.    By 

Herbert   E.    Gregory 467 


PART  I. -MINERALOGY 

EDITED    BY 

S.  L.  PENFIELD 


OF  THE 

UNIVERSITY 

OF 


HISTORY    OF    THE    MINERALOGICAL    DEPART- 
MENT AND   OF  THE  DEVELOPMENT  OF 
MINERALOGY  AT  YALE. 

BY  S.  L.  PENFIELD. 

THE  study  of  Science  at  Yale  may  be  considered  as  having 
had  its  beginning  in  1802,  when  Benjamin  Silliman  was 
appointed  Professor  of  Chemistry  and  Mineralogy  in  the 
College.  The  influence  of  Professor  Silliman  upon  the  early 
development  of  mineralogy  and  in  other  scientific  directions 
at  Yale  was  of  great  importance,  for  he  .  was  a  careful  ob- 
server, an  enthusiastic  teacher,  and  he  had  the  faculty  of 
inspiring  others  with  a  zeal  and  spirit  for  investigation.  Soon 
after  the  appointment  of  Professor  Silliman,  Colonel  George 
Gibbs  of  Rhode  Island,  for  many  years  a  resident  in  Europe, 
returned  from  his  travels  with  a  collection  of  minerals  de- 
scribed as  being  at  that  time  the  most  extensive  and  valuable 
ever  brought  to  this  country.  Professor  Silliman  visited 
Colonel  Gibbs,  spending  much  time  with  him  in  studying 
the  collection,  with  the  result  that  Colonel  Gibbs  made  the 
generous  and  unexpected  proposition  to  open  his  cabinet  at 
Yale  College,  provided  rooms  should  be  fitted  up  for  its 
reception.  To  this  proposition  prompt  response  was  made 
by  the  authorities  of  the  College,  and  in  1810, 1811,  and  1812, 
the  collection  was  arranged  and  placed  at  the  disposition  of 
the  public  under  the  personal  supervision  of  Colonel  Gibbs. 
In  1825  the  collection  was  offered  for  sale,  preference  being 
given  to  Yale  as  purchaser.  Mainly  through  the  influence 
of  Professor  Silliman,  the  necessary  funds  ($20,000)  were 
secured  and  the  collection  became  the  property  of  the 
College,  serving  as  the  nucleus  of  the  present  Yale  College 
Collection. 


4  HISTORY  AND  DEVELOPMENT 

Another  factor  which  has  had  undoubtedly  a  great  in- 
fluence upon  the  development  of  mineralogy  at  Yale  was  the 
founding,  in  1818,  of  the  American  Journal  of  Science  and 
Arts,  at  New  Haven,  by  Professor  Silliman.  Most  American 
contributions  to  mineralogy  have  appeared  in  the  pages  of 
this  journal,  and,  naturally,  the  editors  have  been  consulted 
through  a  long  series  of  years  upon  subjects  pertaining  to 
this  special  department  of  science. 

In  1846,  Benjamin  Silliman,  Jr.,  was  appointed  to  the 
Professorship  of  Applied  Chemistry  and  John  Pitkin  Norton 
to  the  Professorship  of  Agricultural  Chemistry.  In  the  year 
following,  these  gentlemen  opened  an  analytical  laboratory 
for  students  on  the  college  grounds,  in  the  house  formerly 
occupied  by  President  Day.  This  was  the  beginning  of  the 
department  which,  owing  to  the  beneficence  of  the  late 
Joseph  E.  Sheffield  of  New  Haven,  has  since  grown  into 
the  Sheffield  Scientific  School  of  Yale  University.  Chemistry 
and  mineralogy  were,  so  to  speak,  the  corner-stones  upon 
which  the  School  was  built,  and  there  have  always  been 
professors,  instructors,  and  students  in  the  mineralogical  and 
chemical  laboratories  who  have  taken  great  interest  in  min- 
eralogical investigations.  The  long  list  of  papers,  emanating 
in  -the  early  days  of  the  School  from  its  chemical  and  later 
from  its  mineralogical  laboratory,  are  the  strongest  evidence 
which  can  be  produced  of  the  active  part  which  Yale  has 
taken  in  the  development  of  the  science  of  mineralogy. 
These  papers,  a  list  of  which  will  be  found  in  the  bibliogra- 
phy, indicate  the  importance  which  it  has  been  felt  by  those 
connected  with  the  department  should  be  attached  to  the 
chemical  investigation  of  mineral  substances. 

In  1850,  James  D wight  Dana  was  appointed  to  the  Silliman 
Professorship  of  Geology,  and  in  1864,  Mineralogy  was  added 
to  the  title.  While  Professor  Dana's  publications  on  subjects 
pertaining  to  mineralogy  and  crystallography  were  numerous, 
he  was  more  interested  in  the  broader  questions  of  crys- 
tallogeny,  isomorphism,  and  the  classification  of  species, 
than  in  the  details  of  the  characters  of  individual  minerals. 


OF  MINERALOGY  AT  YALE.  5 

His  ability  to  take  the  scattered  observations  of  others  and 
arrange  them  in  concrete,  classified  form  was  remarkable. 
In  1837,  while  assistant  in  the  department  of  chemistry, 
geology,  and  mineralogy  he  published  the  first  edition  of  his 
System  of  Mineralogy,  "  including  an  extended  treatise  on 
crystallography  with  an  appendix  containing  the  applications 
of  mathematics  to  crystallographic  investigation."  Enlarged 
editions  of  the  System  of  Mineralogy  appeared  in  1844,  1850, 
1854,  and  in  1868,  the  last  being  for  many  years  the  standard 
work  on  the  subject,  not  alone  for  America,  but  for  the  world. 
It  was  a  surprise  to  most  scientists  of  Europe  that  a  system 
of  mineralogy,  like  that  of  Professor  Dana's,  could  be  pro- 
duced in  America,  since  at  that  time  there  had  been  very  few 
contributions  to  the  science  of  mineralogy  from  our  country. 
In  1892  Professor  Edward  S.  Dana  entirely  rewrote  and 
much  enlarged  his  father's  work.  This  is  known  as  the 
Sixth  Edition  of  Dana's  System  of  Mineralogy.  These  edi- 
tions of  Dana's  System  of  Mineralogy  have  served  to  make 
Yale  College  known  throughout  the  entire  scientific  world  as 
a  center  for  mineralogy,  and  it  is  doubtful  whether  any  other 
place  at  home  or  abroad  has  exerted  a  like  influence. 

In  1855  a  professorship  of  Metallurgy  was  founded  in  the 
Scientific  School,  and  George  J.  Brush  was  appointed  to  fill 
the  chair.  Professor  Brush,  a  graduate  of  the  class  of  1852, 
had  prepared  himself  by  study  abroad  for  work  along  the  lines 
of  mineralogy,  metallurgy,  and  chemistry,  but  mineralogy  was 
the  subject  which  most  interested  him.  Accordingly  the  title 
of  his  professorship  was  changed  in  1864  to  that  of  mineralogy. 
In  1872  Professor  Brush  became  director  of  the  Sheffield 
Scientific  School,  but  he  retained  his  professorship  of  mineral- 
ogy and  continued  to  give  courses  of  lectures  to  the  students 
until  about  1890.  Although  so  great  a  part  of  his  time  had 
to  be  devoted  to  the  executive  work  demanded  by  his  position 
as  director  of  the  Scientific  School,  he  nevertheless  continued 
his  investigations,  and  conducted  with  the  aid  of  his  students 
important  researches.  He  has  always  taken  an  active  interest 
in  all  investigations  undertaken  in  the  laboratory,  and  has 


6  HISTORY  AND  DEVELOPMENT 

greatly  aided  the  younger  workers  both  by  his  advice  and  also 
by-  supplying  them  with  materials  for  investigation  from  his 
private  collection  of  minerals.  Professor  Brush  published  his 
first  paper  on  mineralogy  in  1850,  when  he  was  a  student  in 
the  old  analytical  laboratory  on  the  college  grounds.  His 
later  publications  are  noted  in  the  bibliography,  with  the 
exception  of  three  important  papers  on  the  Reexamination 
of  American  Minerals,  published  in  1853  with  Professor  J. 
Lawrence  Smith,  with  whom  he  was  associated  for  a  short 
time  at  the  University  of  Virginia.  The  eighth,  ninth  and 
tenth  Supplements  to  the  fourth  edition  of  Dana's  System  of 
Mineralogy  were  prepared  by  Professor  Brush.  He  also  aided 
Professor  Dana  in  the  preparation  of  the  fifth  edition  of  the 
System  of  Mineralogy,  and  afterwards  prepared  the  first 
appendix  to  it.  In  1874  he  published  a  Manual  of  Determi- 
native Mineralogy,  which  has  since  been  very  extensively 
used. 

While  a  student  at  Yale,  Professor  Brush  became  interested 
in  making  a  collection  of  minerals,  and  during  the  period  of 
the  past  fifty  years  his  collection  has  grown  till  it  now  numbers 
over  15,000  specimens.  The  value  of  a  collection,  however, 
must  not  be  estimated  from  the  number  of  specimens  it 
contains,  but  rather  from  its  importance  as  a  means  of 
education  and  from  the  scientific  results  which  have  been 
obtained  from  it.  One  of  the  main  objects  which  Professor 
Brush  has  constantly  kept  in  mind  has  been  to  bring  together 
mineral  specimens  for  purposes  of  study  and  investigation. 
The  Brush  Collection  is  not  on  public  exhibition,  nor  is  it 
intended  that  such  a  disposition  shall  be  made  of  it,  but  for 
convenient  reference  and  study  it  is  kept  in  cabinets  of 
drawers. 

Since  the  foundation  of  the  Sheffield  Scientific  School  the 
collection  has  been  used  for  illustrating  the  lectures  on 
crystallography  and  general  descriptive  mineralogy,  which  are 
given  each  year  to  the  students.  The  collection  is,  moreover, 
a  storehouse  of  material  for  investigation,  and  it  has  an 
inestimable  historical  value,  since  it  contains  the  type  speci- 


OF  MINERALOGY  AT  YALE.  7 

mens  of  the  large  number  of  minerals  which  have  been 
investigated  in  the  mineralogical  and  chemical  laboratories  at 
Yale.  Although  the  collection  and  the  extensive  mineralogical 
library  accompanying  it  are  the  private  property  of  Professor 
Brush,  they  are  deposited  in  the  Peabody  Museum  and  the 
University  has  the  benefit  of  their  full  and  unrestricted  use. 

The  Yale  University  Collection,  of  which  the  Gibbs 
Collection,  already  referred  to,  is  the  nucleus,  is  distinct  from 
the  Brush  Collection.  It  is  contained  in  one  of  the  exhibition 
rooms  of  the  Peabody  Museum,  and  is  in  charge  of  Professor 
Edward  S.  Dana,  who  has  been  Curator  since  1874.  The 
collection,  attractively  displayed,  is  accessible  at  all  times,  not 
only  to  students,  but  also  to  the  public.  It  contains  much 
material  for  study  and  investigation,  and  many  type  specimens 
of  minerals  which  have  been  described.  To  the  Yale  Univer- 
sity Mineral  Collection  belong  also  the  valuable  and  extensive 
Yale  Collection  of  Meteorites  and  the  Blum  Collection  of 
Pseudomorphs.  The  collection  of  pseudomorphs  is  that  of  the 
late  Professor  J.  Reinhard  Blum  of  the  University  of  Heidel- 
berg, purchased  by  Yale  College  in  1872.  Professor  Blum 
was  an  authority  on  the  subject  of  pseudomorphs  and  the 
collection  contains  the  types  described  by  him  in  his  standard 
work,  Die  Pseudomorphosen  des  Mineralreichs. 

Professor  Edward  S.  Dana's  numerous  contributions  to  the 
science  of  mineralogy  are  noted  in  the  bibliography,  and  it  is 
probable  that  his  works,  comprising  the  Sixth  Edition  of 
Dana's  System  of  Mineralogy  (1892),  Text  Book  of  Mineralogy 
(1877  and  1898),  and  Minerals  and  How  to  Study  Them  (1895), 
are  more  extensively  used  than  any  other  books  pertaining  to 
mineralogy.  Professor  Dana  has  also  succeeded  his  father 
and  grandfather  as  Editor  of  the  American  Journal  of  Science. 

In  1873  George  W.  Hawes  was  appointed  Assistant  in 
Mineralogy,  but  he  soon  specialized  along  the  lines  of 
petrography.  His  love  for  science  and  his  enthusiasm  were 
inspirations  to  all  who  knew  him,  and  the  writer  has  always 
considered  it  a  great  privilege  to  have  been  one  of  his  students. 
A  sketch  of  Dr.  Hawes's  life  and  a  bibliography  of  his 


8  HISTORY  AND  DEVELOPMENT 

publications,  prepared  by  Professor  Pirsson,  are  given  in  this 
volume. 

In  1879  the  present  writer,  a  graduate  of  the  class  of  1877, 
and  for  two  years  Assistant  in  Analytical  Chemistry  in  the 
Sheffield  Laboratory,  was  appointed  as  Assistant  in  Mineral- 
ogy. In  1888  he  became  Assistant  Professor,  and  in  1893 
Professor  of  Mineralogy.  In  1898  he  rewrote  and  much 
enlarged  Professor  Brush's  Manual  of  Determinative  Min- 
eralogy and  Blowpipe  Analysis.  At  different  tunes  the  fol- 
lowing men  have  been  associated  with  the  writer  as  assistants 
and  instructors  in  mineralogy :  E.  O.  Hovey,  E.  S.  Sperry, 
O.  C.  Farrington,  L.  V.  Pirsson,  J.  H.  Pratt,  C.  H.  Warren, 
and  W.  E.  Ford.  The  devotion  of  these  men  to  their  work, 
and  their  love  for  science,  have  rendered  possible  the  publi- 
cation of  the  long  series  of  investigations  which  are  cited  in 
the  bibliography. 

Most  cordial  relations  have  always  existed  between  the 
departments  of  chemistry  and  mineralogy  in  the  Sheffield 
Scientific  School.  In  the  early  days  of  the  school  mineral 
analyses  were  all  made  in  the  Sheffield  Chemical  Laboratory, 
and  it  was  not  until  1881  that  a  special  analytical  laboratory 
was  provided  for  the  mineralogical  department.  Professor 
H.  L.  Wells,  a  graduate  of  the  class  of  1877,  was  appointed 
instructor  in  Analytical  Chemistry  in  1884,  and  in  1888  he 
became  Assistant  Professor,  in  1893  Professor  of  Analytical 
Chemistry  and  Metallurgy.  In  addition  to  his  investigations 
in  chemistry  he  has  made  many  important  contributions  to 
mineralogy,  as  may  be  seen  from  the  titles  given  in  the  biblio- 
graphy. Dr.  H.  W.  Foote,  also  of  the  chemical  department, 
has  contributed  much  to  our  knowledge  of  the  chemical  com- 
position of  minerals.  Many  of  the  papers  of  Professor  Wells 
and  of  Dr.  Foote  appear  in  full  in  the  pages  of  this  volume. 
On  the  other  hand  those  connected  with  the  mineralogical 
department  have  devoted  much  time  to  the  examination  of 
crystals  of  new  and  rare  compounds  made  in  the  chemical  labo- 
ratory. Thus  the  two  departments  help  and  supplement  one 
another,  for  chemistry  and  crystallography  are  essential  to  both. 


OF  MINERALOGY  AT  YALE.  9 

The  bibliography  which  follows  will  serve  to  give  some 
idea  of  the  character  of  the  investigations  undertaken,  and  of 
the  amount  of  work  accomplished  in  the  Yale  Laboratories. 
Following  the  bibliography  are  three  Summaries  of  the  more 
important  results:  the  first  of  these  gives  the  new  species 
described;  the  second  the  minerals  whose  chemical  formulas 
have  been  determined;  and  the  third  the  minerals  whose 
crystalline  characters  have  been  established. 

BIBLIOGRAPHY  OF   MINERALOGICAL    PAPERS    FROM    THE 
LABORATORIES  OF  YALE   UNIVERSITY. 

1849.  Analysis  of  Indianite  (Anorthite)  ;  by  G.  J.  Brush.     Amer.  Jour. 

Sci.  (2),  vol.  8,  p.  391. 

1850.  Analyses  of  American  Spodumene;  by  G.  J.  Brush.     Ibid.,  vol. 

10,  pp.  370-371. 
1852.   Fluor-spar  of  Gallatin  Co.,  111.  ;  by  G.  J.  Brush.     Ibid.,  vol.  14, 

p.  112. 
1854.    On  the   Chemical  Composition  of  Clintonite;  by  G.  J.    Brush. 

Ibid.,  vol.  18,  pp.  407-409. 

1857.  Analysis  of  Antigorite  (Serpentine)  ;  by  G.  J.  Brush.     Ibid.,  vol. 

24,  p.  128. 

1858.  On  Chalcodite;   by  G.   J.   Brush.     Ibid.,   vol.    25,   pp.   198-201. 
Mineralogical    Notices    (Gieseckite,    Pyrophyllite,   Unionite    and 

Orthoclase);  by  G.  J.  Brush.     Ibid.,  vol.  26,  pp.  64-70. 

1859.  On  Boltonite;  by  G.  J.  Brush.     Ibid.,  vol.  27,  pp.  395-398. 

1860.  Eighth   Supplement  to  the  4th   Edition  of  Dana's  Mineralogy; 

by  G.  J.  Brush.     Ibid.,  vol.  29,  pp.  363-383. 

1861.  Ninth  Supplement  to  the  4th  Edition  of  Dana's  Mineralogy ;  by 

G.  J.  Brush.     Ibid.,  vol.  31,  pp.  354-371. 
On  the  Crystalline  Form  of  the  Hydrate  of  Magnesia  (Brucite) 

from  Texas  in  Pennsylvania;  by  G.  J.  Brush.     Ibid.,  vol.  32, 

pp.  94-95. 
The  Gold  of  Nova  Scotia;  by  O.  C.  Marsh.    Ibid.,  vol.  32,  pp. 

395-400. 

1862.  Tenth  Supplement  to  the  4th  Edition  of  Dana's  Mineralogy;  by 

G.  J.  Brush.    Ibid.,  vol.  34,  pp.  202-224. 
On  Amblygonite  from  Hebron,  in  Maine ;  by  G.  J.  Brush.     Ibid., 

vol.  34,  pp.  243-245. 
On  the  Occurrence  of  Triphyline  at  Norwich,  in  Massachusetts ; 

by  G.  J.  Brush.     Ibid.,  vol.  34,  p.  402. 

1863.  Catalogue  of  Mineral  Localities  in  New  Brunswick,  Nova  Scotia 


10  HISTORY  AND  DEVELOPMENT 

and  Newfoundland;  by  O.  C.  Marsh.     Ibid.,  vol.  35,  pp.  210- 

218. 
On  Childrenite  from  Hebron  in  Maine ;  by  G.  J.  Brush.     Ibid., 

vol.  36,  p.  257. 
On  Tephroite,  by  G.  J.  Brush.     Ibid.,  vol.  37,  pp.  66-70. 

1865.  On  Crystallized  Diopside  as  a  Furnace  Product ;  by  G.  J.  Brush. 

Ibid.,  vol.  39,  pp.  132-134. 

1866.  Mineralogical  Notices  (On  Cookeite  and  Jefferisite,  new  mineral 

species)  ;  by  G.  J.  Brush.     Ibid.,  vol.  41,  pp.  246-248. 

A  Method  of  Giving  and  of  Measuring  the  angles  of  Crystals,  for 
the  determination  of  species,  by  the  use  of  the  Reflecting  Gonio- 
meter ;  by  J.  M.  Blake.  Ibid.,  vol.  41,  pp.  308-311. 

On  Gay-Lussite  from  Nevada  Territory ;  by  B.  Silliman.  Ibid., 
vol.  42,  pp.  220-221. 

On  Crystals  of  Gay-Lussite  from  Nevada  Territory ;  by  J.  M. 
Blake.  Ibid.,  vol.  42,  pp.  221-222. 

1867.  On  Kaolinite  and  Pholerite ;  by  S.  W.  Johnson  and  J.  M.  Blake. 

Ibid.,  vol.  43,  pp.  351-361. 
Crystallogenic  and  Crystallographic  Contributions ;  by  J.  D.  Dana. 

Ibid.,  vol.  44,  pp.  89-95. 
On  Mineralogical  Nomenclature;  by  J.  D.  Dana.     Ibid.,  vol.  44, 

pp.  145-151. 
Observations  on  the  Native   Hydrates  of  Iron;  by  G.  J.  Brush, 

with  analyses  of  Turgite  by  C.  S.  Rodman.     Ibid.,  vol.  44,  pp. 

219-222. 
Crystallogenic  and  Crystallographic  Contributions ;  by  J.  D.  Dana. 

Ibid.,  vol.  44,  pp.  252-263. 

Contributions  to  the  Mineralogy  of  Nova  Scotia  (Lederite  identi- 
cal with  Gmelinite)  ;  by  O.  C.  Marsh.  Ibid.,  vol.  44,  pp.  362- 

367. 
Crystallogenic  and  Crystallographic  Contributions;  byj.  D.  Dana. 

Ibid.,  vol.  44,  pp.  398-409. 

1868.  Contributions  to  Mineralogy  (  Enargite  from  Colorado,  Argenti- 

ferous Jamesonite,  Argentiferous  Tetrahedrite)  ;  by  B.  S.  Bur- 
ton. Ibid.,  vol.  45,  pp.  34-38. 

On  Willemite  and  Tephroite;  by  W.  G.  Mixter.  Ibid.,  vol.  46, 
pp.  230-232. 

On  Sussexite,  a  new  borate  from  Mine  Hill,  Franklin  Furnace, 
Sussex  Co.,  New  Jersey;  by  G.  J.  Brush.  Ibid.,  vol.  46,  pp. 
240-243. 

The  fifth  Edition  of  Dana's  System  of  Mineralogy.  By  J.  D. 
Dana,  aided  by  G.  J.  Brush,  p.  827. 

1869.  On  Hortonolite,  a  new  member  of  the  Chrysolite  group  ;  by  G. 

J.  Brush.     With  measurements  and  observations  on  the  crys- 


OF  MINERALOGY  AT  YALE.  11 

talline  form  of  the  mineral;  by  J.  M.  Blake.     Amer.  Jour.  Sci., 

vol.  48,  pp.  17-23. 
On  Durangite,  a  fluo-arsenate  from  Durango  in  Mexico  ;  by  G.  J. 

Brush.     Ibid.,  vol.  48,  pp.  179-182. 
On  the  Meteoric  Stone  which  fell  Dec.  5th,  1868  in  Franklin  Co., 

Alabama;  by  G.  J.  Brush.     Ibid.,  vol.  48,  pp.  240-244. 
On  the  Magnetite  in  the  mica  of  Pennsbury,  Pa.,  in  reply  to  Prof. 

G.  Rose;  by  J.  D.  Dana  and  G.  J.  Brush.     Ibid.,  vol.  48,  pp. 

360-362. 

1871.  On  Gahnite  from  Mine  Hill,  Franklin  Furnace,  New  Jersey;  by 

G.  J.  Brush.     Ibid.  (3),  vol.  1,  pp.  28-29. 

On  Ralstonite,  a  new  Fluoride  from  Arksuk-fiord ;  by  G.  J. 
Brush.  Ibid.,  vol.  2,  pp.  30-31. 

1872.  First  Appendix  to  the  5th  Edition  to  Dana's  Mineralogy ;  by  G. 

J.  Brush,     p.  19. 
On  the  Datolite  from  Bergen  Hill,  New  Jersey ;  by  E.  S.  Dana. 

Amer.  Jour.  Sci.,  (3),  vol.  4,  pp.  16-22,  with  one  plate. 
On  a  Crystal  of  Andalusite,  from  Delaware  Co.,  Pa. ;    by  E.  S. 

Dana.  Ibid.,  vol.  4,  p.  473. 

1873.  On  a  compact  Anglesite  from  Arizona;    by  G.  J.  Brush.     Ibid. 

vol.  5,  pp.  421-422. 

On  the  Minerals  found  at  the  Tilly  Foster  Iron  Mine,  Brew- 
sters,  N.  Y.  (Mica,  Chlorite,  Serpentine,  Enstatite,  Actinolite, 
Chondrodite)  ;  by  E.  S.  Breidenbaugh.  Ibid.,  vol.  6,  pp. 
207-213. 

1874.  Manual    of    Determinative  Mineralogy  and   Blowpipe   Analysis, 

with  Tables  for  the  identification  of  Minerals  ;  by  G.  J.  Brush. 

p.  104. 
On  a  Feldspar  (Oligoclase)  from  Bamle  in   Norway ;   by  G.  W. 

Hawes.     Amer.  Jour.    Sci.  (3),  vol.  7,  p.  579. 
On  the  Thermo-Electrical  Properties  of  some  Minerals  and  their 

varieties;   by  A.  Schrauf  and  E.  S.  Dana.     Ibid.,  vol.  8,  pp. 

255-267. 
On   Serpentine  Pseudomorphs,  and  other  kinds,  from  the  Tilly 

Foster  Iron  Mine,  Putnam  Co.,  N.  Y. ;  by  J.  D.  Dana.     Ibid., 

vol.  8,  pp.  371-381,  and  447-459,  with  two  plates. 

1875.  On  Zonochlorite  and  Chlorastrolite  ;  by  G.  W.  Hawes.     Ibid.,  vol. 

10,  pp.  24-26. 

On  the  Chondrodite  from  the  Tilly  Foster  Iron  Mine,  Brewsters, 
N.  Y.;  by  E.  S.  Dana.  Ibid.,  vol.  10,  pp.  89-103,  with  three 
plates. 

1876.  On   the  Optical  Character   of  the   Chondrodite  from  the  Tilly 

Foster  Mine,  Brewsters,  N.  Y. ;  by  E.  S.  Dana.     Ibid.,  vol.  11, 
pp.  139-140. 


12  HISTORY  AND  DEVELOPMENT 

On  the  Samarskite  of  Mitchell  Co.,  North  Carolina;    by  E.   S. 

Dana.     Ibid.,  vol.  11,  pp.  201-204. 
On  new  twins  of  Staurolite  and  Pyrrhotite ;  by  E.  S.  Dana.     Ibid., 

vol.  11,  pp.  384-388. 
On  a  Lithia-bearing  variety  of  Biotite;  by  G.  W.  Hawes.     Ibid., 

vol.  11,  pp.  431-432. 
On  the   Chemical  Composition   of   Durangite  ;   by  G.  J.  Brush. 

Ibid.,  vol.  11,  pp.  464-465. 
On  the  Association  of  Crystals  of  Quartz  and  Calcite  in  parallel 

position,  as    observed  in   a    Specimen   from   the    Yellowstone 

Park;  by  E.  S.  Dana.     Ibid.,  vol.  12,  pp.  448-451. 

1877.  On  grains  of  Metallic  Iron  in  Dolerytes  from  New  Hampshire  ;  by 

G.  W.  Hawes.     Ibid.,  vol.  13,  pp.  33-35. 
On  the  Chemical  Composition  of  Triphylite  from  Grafton,  New 

Hampshire;  by  S.  L.  Penfield.     Ibid. !|  vol.  13,  pp.  425-427. 
On  the  Chemical  Constitution  of   Hatchettolite  and  Samarskite, 

from  Mitchell  Co.,  North  Carolina;  by  O.  D.  Allen.     Ibid.,  vol. 

14,  pp.  128-131. 
On  the  occurrence  of  Garnets  with  the  Trap  of  New  Haven  ;  by 

E.  S.  Dana.     Ibid.,  vol.  14,  pp.  215-218. 

1878.  On   a  new  and    remarkable    Mineral   locality    in    Fairfield    Co., 

Connecticut ;  with  a  description  of  several  new  species  occur, 
ring  there  (Eosphorite,  Triploidite,  Dickinsonite,  Lithiophilite, 
Reddingite)  ;  by  G.  J.  Brush  and  E.  S.  Dana.  First  paper. 
Ibid.,  vol.  16,  pp.  33-46  and  114-123. 

1879.  On  the  Chemical  Composition  of  Triphylite;  by  S.  L.  Penfield. 

Ibid.,  vol.  17,  pp.    226-229. 
On  the  Presence   of   Chlorine  in   Scapolites ;    by  F.  D.  Adams. 

Ibid.,  vol.  17,  pp.  315-320. 
On  the  Mineral  locality  in  Fairfield  Co.,  Connecticut,  with  the 

description  of  two  additional  new  species  (Fairfieldite,  Fillo- 

wite) ;  by  G.  J.  Brush  and  E.  S.  Dana.     Second  Paper.     Ibid., 

vol.  17,  pp.  359-368. 
Analysis  of  the  Tetrahedrite  from   Huallanca,  Peru ;    by  W.  J. 

Comstock.     Ibid ,  vol.  17,  pp.  401-402. 
On  the  Mineral  Locality  in  Fairfield  Co.,  Connecticut;    by  G. 

J.  Brush  and  E.  S.  Dana.     Third  Paper.     Ibid.,  vol.  18,  pp. 

45-50. 
On  the  Chemical  Composition  of  Amblygonite  ;  by  S.  L.  Penfield. 

Ibid.,  vol.  18,  pp.  295-301. 

1880.  Analyses  of  some   American   Tantalates;    by  W.  J.  Comstock. 

Ibid.,  vol.  19,  pp.  131-132. 

On  the  Chemical  Composition  of  the  Uraninite  from  Branchville, 
Conn. ;  by  W.  J.  Comstock.     Ibid.,  vol.  19,  pp.  220-222. 


OF  MINERALOGY  AT  YALE.  13 

On  the  Chemical  Composition  of  Childrenite ;  by  S.  L.  Penfield. 

Ibid.,  vol.  19,  pp.  315-317. 

Analyses  of  some  Apatites  containing  Manganese  ;  by  S.  L.  Pen- 
field.     Ibid.,  vol.  19,  pp.  367-369. 
Bastnasite  and  Tysouite  from  Colorado ;  by  O.  D.  Allen  and  W.  J. 

Comstock.     Ibid.,  vol.  19,  pp.  390-393. 
On  Crystallized  Danburite  from  Russell,  St.  Lawrence  Co.,  New 

York;   by  G.  J.  Brush  and   E.    S.  Dana.     Ibid.,  vol.  20,  pp. 

111-118. 
On  the  Mineral  Locality  at  Branchville,  Connecticut  (Spodumerie 

arid  the  results  of  its  Alteration)  ;  by  G.  J.  Brush  and  E.  S.  Dana. 

Fourth  Paper.     Ibid.,  vol.  20,  pp.  257-285,  with  one  plate. 

1881.  On  Liquid  Carbon  Dioxide  in  Smoky  Quartz  ;  by  G.  W.  Hawes. 

Ibid.,  vol.  21,  pp.  203-209. 
On  the  Gaseous  Substances   contained  in  the  Smoky  Quartz  of 

Branchville,  Conn.;    by   A.  W.   Wright.     Ibid.,  vol.  21,   pp. 

209-216. 
On  American  Sulpho-Selenides  of  Mercury  ;  by  G.  J.  Brush,  with 

Analyses  of  Onofrite  from  Utah;  by  W.  J.  Comstock.     Ibid., 

vol.  21,  pp.  312-316. 
On  the   Emerald-green   Spodumene  from   Alexander  Co.,  North 

Carolina;  by  E.  S.  Dana.     Ibid.,  vol.  22,  pp.  179-182. 

1882.  On  Crystals  of  Monazitefrom  Alexander  Co.,  North  Carolina;  by 

E.  S.  Dana.     Ibid.,  vol.  24,  pp.  247-250. 

On  the  Occurrence  and  Composition  of  some  American  varieties  of 
Monazite  ;  by  S.  L.  Penfield.  Ibid.,  vol.  24,  pp.  250-254. 

1883.  On  Scovillite,  a  new  phosphate  of  Didymium,  Yttrium  and  other 

rare  earths,  from  Salisbury,  Conn.  ;  by  G.  J.  Brush  and  S.  L. 

Penfield.     Ibid.,  vol.  25,  pp.  459-463. 
Analyses  of  two  varieties  of   Lithiophilite  ;    by  S.  L.   Penfield. 

Ibid.,  vol.  26,  p.  176. 
On  the  Stibnite  from  Japan  ;  by  E.  S.  Dana.     Ibid.,  vol.  26,  pp. 

214-221. 
On   a  variety  of  Descloizite  from  Mexico ;    by   S.   L.  Penfield. 

Ibid.,  vol.  26,  pp.  361-365. 

1884.  On  the  identity  of  Scovillite  with  Rhabdophane;  by  G.  J.  Brush 

and  S.  L.  Penfield.     Ibid.,  vol.  27,  pp.  200-201. 

On  the  Crystalline  Form  of  the  supposed  Herderite  from  Stone- 
ham,  Maine;  by  E.  S.  Dana.  Ibid.,  vol.  27,  pp.  229-232. 

Mineralogical  Notes  (Allanite,  Apatite,  Tysonite)  ;  by  E.  S.  Dana. 
Ibid.,  vol.  27,  pp.  479-481. 

On  the  occurrence  of  Alkalies  in  Beryl  ;  by  S.  L.  Penfield.  Ibid., 
vol.  28,  pp.  25-32. 

A  Crystallographic  Study  of  the  Thinolite  of  Lake  Lahontan ;  by 


14  HISTORY  AND  DEVELOPMENT 

E.   S.  Dana.     Bull.   No.   12.   U.   S.   Geolog.   Survey,   27  pp. 
2  plates. 

1885.  Crystallized  Tiemannite  and  Metacinnabarite ;  by  S.  L.  Penfield. 

Amer.  Jour.  Sci.,  vol.  29,  pp.  449-454. 
On  the  Gahnite  of  Rowe,  Massachusetts  ;  by  A.  G.  Dana.     Ibid., 

vol.  29,  pp.  455-456. 
Gerhardtite  and  Artificial  Basic  Cupric  Nitrates ;  by  H.  L.  Wells 

and  S.  L.  Penfield.     Ibid.,  vol.  30,  pp.  50-57. 
On  the.occurrence  of  Fayalite  in  the  Lithophyses  of  Obsidian  and 

Rhyolite  in  the  Yellowstone  National  Park ;  by  J.  P.  Iddings. 

Crystallographic  study  of  the   Fayalite ;    by   S.   L.   Penfield. 

Ibid.,  vol.  30,  pp.  58-60. 
Crystals  of  Analcite  from  the  Phoenix  Mine,  Lake  Superior  Copper 

Region ;  by  S.  L.  Penfield.     Ibid.,  vol.  30,  pp.  112-113. 
Mineralogical  Notes  (Hanksite,  Lead  Silicate);  by  E.  S.  Dana  and 

S.  L.  Penfield.     Ibid.  vol.  30,  pp.  136-139. 
The   Quantitative  Determination   of  Niobium  (with  analysis  of 

Columbite  from  Branchville,  Conn.)  ;  by  T.  B.  Osborne.     Ibid., 

vol.  30,  pp.  329-337. 

1886.  Brookite  from  Magnet  Cove,  Arkansas ;  by  S.  L.  Penfield.     Ibid., 

vol.  31,  pp.  387-389. 
On  the  Chemical  Composition  of  Herderite  and  Beryl,  with  note 

on  the  Precipitation  of  Aluminium  and  Separation  of  Beryllium 

and  Aluminium;  by  S.  L.  Penfield  and  D.  N.  Harper.     Ibid., 

vol.  32,  pp.   107-117. 
On  the  Crystallization  of  Gold  ;  by  E.  S.  Dana.     Ibid.,  vol.  32, 

pp.  132-138. 
On  two  hitherto  undescribed  Meteoric  Stones;  by  E.  S.  Dana  and 

S.  L.  Penfield.     Ibid.,  vol.  32,  pp.  226-231. 
On  Pseudomorphs   of   Garnet  from  Lake   Superior   and  Salida, 

Colorado;  by  S.  L.  Penfield  and  F.  L.  Sperry.     Ibid.,  vol.  32, 

pp.  307-311. 
On  the  Brookite  from  Magnet  Cove,  Arkansas ;  by  E.  S.  Dana. 

Ibid.,  vol.  32,  pp.  314-317,  with  two  plates. 
On  the  Chemical  Composition  of   Ralstonite;    by  S.  L.  Penfield 

and  D.  N.  Harper.     Ibid.,  vol.  32,  pp.  380-385. 
Mineralogical  Notes  (Columbite,  Diaspore,  Zincite,  Sulphur)  ;  by 

E.  S.  Dana.     Ibid.,  vol.  32,  pp.  386-390. 
On  the  Crystallization  of  Native  Copper  ;  by  E.  S.  Dana.    Ibid., 

vol.  32,  pp.  413-428,  with  four  plates. 
Ueber  den  Columbit ;  by  E.  S.  Dana.     Zeitschr.  Kryst.,  vol.  12, 

pp.  266-274. 

1887.  Phenacite  from  Colorado;  by  S.  L.  Penfield.     Amer.  Jour.  Sci., 

vol.  33,  pp.  130-134. 


OF  MINERALOGY  AT  YALE.  15 

On  the  Topaz  from  the  Thomas  Range,  Utah;  by  A.  N.  Ailing. 

Ibid.,  vol.  33,  pp.  146-147. 
Contributions  to  Mineralogy  (Rutile,  Apatite,  Beryl,  Tourmaline, 

Quartz,   Topaz,   Corundum)  ;    by  W.   E.    Hidden   and    H.   S. 

Washington.     Ibid.,  vol.  33,  pp.  501-507. 
On  the  Chemical  Composition  of  Howlite,  with  a  note  on  the  Gooch 

method  for  the  determination  of  boracic  acid ;  by  S.  L.  Peufield 

and  E.  S.  Sperry.     Ibid.,  vol.  34,  pp.  220-223. 
Bismutosphserite  from   Willimantic  arid  Portland,  Connecticut; 

by  H.  L.  Wells.     Ibid.,  vol.  34,  pp.  271-274. 
Triclinic   Feldspars  with  twinning  striations  on  the  brachypin- 

acoid;   by  S.  L.  Penfield  and  F.  L.  Sperry.     Ibid.,  vol.   34, 

pp.  390-393. 

1888.  On  the  Law  of  Double  Refraction  in  Iceland  Spar  ;  by  C.  S.  Hast- 

ings.    Ibid.,  vol.  35,  pp.  60-73. 
On  the  Crystalline  form  of  Polianite  ;  by  E.  S.  Dana  and  S.  L. 

Penfield.     Ibid.,,  vol.  35,  pp.  243-247. 
Notes  on  certain  rare  Copper  Minerals   from  Utah  (Olivenite, 

Erinite,  Tyrolite,  Chalcophyllite,  Clinoclasite,  Mixite,  Brochan- 

tite)  ;  by  W.  F.  Hillebrand  and  H.  S.  Washington.     Ibid.,  vol. 

35,  pp.  298-307. 
Bertrandite  from  Mt.  Antero,  Colorado;  by  S.  L.  Penfield.     Ibid., 

vol.  36,  pp.  52-55. 
Preliminary  notice  of  Beryllonite,  a  new  mineral ;  by  E.  S.  Dana. 

Ibid.,  vol.  36,  pp.  290-291. 
Mineralogical  Notes  (Beryl,  Phenacite,  Monazite,  Sussexite,  Twin 

Crystals  of  Quartz,  Oligoclase,  Barium  Feldspar,  Phlogopite)  ; 

by    S.   L.   Penfield    and    E.    S.    Sperry.      Ibid.,  vol.   36,  pp. 

317-331. 

1889.  Description  of  the  new  Mineral  Beryllonite;  by  E.  S.  Dana  and 

H.  L.  Wells.     Ibid.,  vol.  37,  pp.  23-32,  with  one  plate. 
Sperrylite,   a  new  Mineral;    by  H.    L.   Wells.     Ibid.,   vol.    37, 

pp.  67-70. 
On  the  Crystalline  Form  of  Sperrylite  •,  by  S.  L.  Penfield.     Ibid., 

vol.  37,  pp.  71-73. 
On  some  curiously  developed  Pyrite  Crystals  from  French  Creek, 

Chester  Co.,  Pennsylvania;   by  S.  L.  Penfield.     Ibid.,  vol.  37, 

pp.   209-212. 
Crystallized  Bertrandite  from  Stoneham,  Maine  and  Mt.  Antero, 

Colorado  ;  by  S.  L.  Penfield.     Ibid.,  vol.  37,  pp.  213-216. 
Notes  on  the  Crystallization  of   Trona  (Urao)  ;  by  E.  F.  Ayres. 

Ibid.,  vol.  38,  pp.  65-66. 
Results  Obtained  by  Etching  a  Sphere  and  Crystals  of  Quartz  with 

Hydrofluoric  Acid ;  by  O.  Meyer  and  S.  L.  Penfield.     Transac. 

Conn.  Acad.,  vol.  8,  pp.  158-165,  with  two  plates. 


16  HISTORY  AND  DEVELOPMENT 

1890.  On  the  Barium  Sulphate  from  Perkins  Mill,  Templeton,  Province 

of  Quebec  ;  by  E.  S.   Dana.     Amer.  Jour.   Sci.,   vol.   39,  pp. 

61-65. 
On  Lansfordite;     Nesquehonite,  a  new  Mineral;    and  Pseudo- 

morphs  of  Nesquehonite  after  Lansfordite  ;  by  F.  A.  Genth  and 

S.  L.  Penfield.    Ibid.,  vol.  39,  pp.  121-137,  with  one  plate. 
On  the    Mineral    Locality  at  Branchville,    Connecticut  :     Fifth 

Paper  ;    by  G.  J.  Brush  and  E.  S.  Dana.     With   analyses  of 

several  manganesian  phosphates;  by  H.  L.  Wells.    Ibid.,  vol.  39, 

pp.  201-216. 
Additional  Notes  on  the  Tyrolite  from  Utah ;  by  W.  F.  Hillebrand 

and  E.  S.  Dana.     Ibid.,  vol.  39,  pp.  271-273. 
On  Spangolite,  a  new  Copper  Mineral ;  by  S.  L.  Penfield.     Ibid., 

vol.  39,  pp.  370-378. 
On  Hamlinite,  a  new  rhombohedral  Mineral  from  the  Herderite 

locality  at  Stoneham,  Maine;  by  W.  E.  Hidden  and  S.  L.  Pen- 
field.     Ibid.,  vol.  39,  pp.  511-513. 
Fayalite  in  the  Obsidian  of  Lipari ;  by  J.  P.  Iddings  and  S.  L. 

Penfield.     Ibid.,  vol.  40,  pp.  75-78. 
On  some  Selenium  and  Tellurium  minerals  from  Honduras  (Selen- 

Tellurium,  Durdenite) ;  by  E.  S.  Dana  and  H.  L.  Wells.    Ibid., 

vol.  40,  pp.  78-82. 
Crystallographic  Notes  (Amarantite,  Sideronatrite,  Ferronatrite) 

by  S.  L.  Penfield.     Ibid.,  vol.  40,  pp.  199-203. 
Chalcopyrite  Crystals  from  the  French  Creek  Iron  Mines,  St.  Peter, 

Chester  Co.,  Pennsylvania;  by  S.  L.  Penfield.     Ibid.,  vol.  40, 

pp.  207-211. 

On  Mordenite  ;  by  L.  V.  Pirsson.     Ibid.,  vol.  40,  pp.  232-237. 
Analysis  of  Rhodochrosite  from  Franklin  Furnace,  New  Jersey; 

by  P.  E.  Browning.     Ibid.,  vol.  40,  pp.  375-376. 
Anthophyllite  from  Bakersville,  Mitchell  Co.,  North  Carolina;  by 

S.  L.  Penfield.    Ibid.,  vol.  40,  pp.  394-397. 
On   the  so-called   Perofskite    (Dysanalyte)   from    Magnet   Cove, 

Arkansas  ;  by  F.  W.  Mar.     Ibid.,  vol.  40,  pp.  403-405. 
On  the   Fowlerite  variety  of  Rhodochrosite  from  Franklin  and 

Sterling,  New  Jersey  ;  by  L.  V.  Pirsson.    Ibid.,  vol.  40,  pp.  484- 

488. 
Some  Observations  on  the  Beryllium  Minerals  from  Mt.  Antero, 

Colorado  (Beryl,  Bertrandite,  Phenacite) ;   by  S.  L.  Penfield. 

Ibid.,  vol.  40,  pp.  488-491. 

1891.  On  some  remarkably  developed  Calcite  Crystals ;  by  L.  V.  Pirsson. 

Ibid.,  vol.  41,  pp.  61-64. 

On  the  Chemical  Composition  of  Aurichalcite ;  by  S.  L.  Penfield. 
Ibid.,  vol.  41,  pp.  106-109. 


OF  MINERALOGY  AT  YALE.  17 

On  the  Composition  of  Pollucite  and  its  Occurrence  at  Hebron, 

Maine;  by  H.  L.  Wells.     Ibid.,  vol.  41,  pp.  213-220. 
On   Crystallized  Azurite   from   Arizona ;   by   O.    C.    Farrington. 

Ibid.,  vol.  41,  pp.  300-307. 
Contributions  to   Mineralogy;   by  F.    A.    Genth;   with   Crystal- 

lographic  Notes;  by  S.  L.  Penfield  and  L.  V.  Pirsson  (Axinite, 

Eudialyte,    Titanite,   Monticellite).      Ibid.,   vol.  41,   pp.    394- 

400. 
Columbite  from  the  Black  Hills,  South  Dakota;  by  W.  P.  Blake; 

with  Crystallographic  Notes;  by  S.  L.  Penfield.     Ibid.,  vol.  41, 

pp.  403-405. 
The  Minerals  in  Hollow  Spherulites  of  Rhyolite  from  Glade  Creek, 

Wyoming;  by  J.  P.  Iddings  and  S.  L.  Penfield.      Ibid.,  vol. 

42,  pp.  39-46. 
Gmelinite  from  Nova  Scotia;  by  L.  V.  Pirsson.     Ibid.,  vol.  42, 

pp.  57-63. 
Occurrence  of  Sulphur,  Orpiment,  and  Realgar  in  the  Yellowstone 

National  Park  ;  by  W.  H.  Weed  and  L.  V.  Pirsson.     Ibid.,  Vol. 

42,  pp.  401-405. 
Mineralogical  Notes  (Cerussite,  Hematite  and  Cassiterite,  Gypsum, 

Pennine)  ;  by  L.  V.  Pirsson.     Ibid.,  vol.  42,  pp.  405-409. 
1892.   The  Chemical  Composition  of  lolite  ;  by  O.  C.  Farrington.     Ibid., 

vol.  43,  pp.  13-16. 
On  a  Series  of  Caesium  Trihalides ;  by  H.  L.  Wells.     Including 

their  Crystallography ;   by  S.  L.  Penfield.      Ibid.,  vol.  43,  pp. 

17-32. 
Crystallographic  Notes  on  Hiibnerite;  by  S.  L.  Penfield.     Ibid., 

vol.  43,  pp.  184-187. 
On  the  Rubidium  and  Potassium  Trihalides  ;  by  H.  L.  Wells  and 

H.  L.  Wheeler.     With  their  Crystallography;  byS.  L.  Penfield. 

Ibid.,  vol.  43,  pp.  475-487. 
On  Polybasite  and  Tennantite  from  the  Mollie  Gibson  Mine  in 

Aspen,  Colorado;  by  S.  L.  Penfield  and  S.  H.  Pearce.     Ibid., 

vol.  44,  pp.  15-18. 
On  the  Alkali-Metal  Pentahalides ;  by  H.  L.  Wells  and  H.  L. 

Wheeler.     With  their  Crystallography ;  by  S.  L.  Penfield.     Ibid., 

vol.  44,  pp.  42-49. 
On  Herderite  from  Hebron,  Maine;  by  H.  L.  Wells  and  S.  L. 

Penfield.     Ibid.,  vol.  44,  pp.  114-116. 

On  some  Alkaline  lodates ;   by  H.  L.  Wheeler.     With  Crystal- 
lographic Notes;  byS.  L.  Penfield.    Ibid.,  vol.  44,  pp.  123-133. 
On  some  Double  Halides  of  Silver  and  the  Alkali  Metals ;  by  H. 

L.  Wells  and  H.  L.  Wheeler.     With  their  Crystallography;  by 

S.  L.  Penfield.     Ibid.,  vol.  44,  pp.  155-157. 
2 


18  HISTORY  AND  DEVELOPMENT 

On  the  Caesium  and  Rubidium  Chloraurates  and  Bromaurates ;  by 

H.  L.  Wells  and  H.  L.  Wheeler.     With  their  Crystallography ; 

by  S.  L.  Penfield.     Ibid.,  vol.  44,  pp.  157-162. 
On  the  Crystallography  of  the  Caesium-Mercuric  Halides;  by  S. 

L.  Penfield.     Ibid.,  vol.  44,  pp.  311-321. 
Crystallographic   Notes   (Rutile,   Danalite) ;    by  S.   L.   Penfield. 

Ibid.,  vol.  44,  pp.  384-386. 
Sixth  Edition  of  Dana's  Mineralogy.    Entirely  rewritten  and  much 

enlarged ;  by  E.  S.  Dana.     1134  pp. 

1893.  Datolite  from  Loughboro,  Ontario  ;  by  L.  V.  Pirsson.     Amer. 

Jour.  Sci.,  vol.  45,  pp.  100-102. 
On  the  Crystallization  of  the  Double  Halides  of  Tellurium  with 

Potassium,  Rubidium  and  Caesium;  by  H.  L.  Wheeler.     Ibid., 

vol.   45,  pp.  267-279. 
On  Cookeite  from  Paris  and  Hebron,  Maine;  by  S.  L.  Penfield. 

Ibid.,  vol.  45,  pp.  393-396. 
Mineralogical  Notes   (Zunyite,  Xenotime)  ;    by  S.   L.   Penfield. 

Ibid.,  vol.  45,  pp.  396-399. 
On  Pentlandite  from  Sudbury,  Ontario,  Canada,  with   Remarks 

upon  three  supposed  new  species  from  the  same  region ;  by  S.  L. 

Penfield.     Ibid.,  vol.  45,  pp.  493-497. 
On  the  Crystallization  of  the  Double   Halides   of   Arsenic  with 

Caesium  and  Rubidium,  and  of  some  Compounds  of  Arsenious 

Oxide  with  Halides  of  Caesium,  Rubidium,  and  Potassium ;  by 

H.  L.  Wheeler.     Ibid.,  vol.  46,  pp.  88-98. 
On   Canfieldite,  a  new  Germanium   Mineral    (later  shown  to  be 

Argyrodite)  and  on  the  Chemical  Composition  of  Argyrodite  ; 

by  S.  L.  Penfield.     Ibid.,  vol.  46,  pp.  107-113. 
On  some  Minerals  from  the  Manganese  Mines  of  St.  Marcel,  in 

Piedmont,  Italy  (Alurgite,  Pyroxene,  Violan)  ;  by  S.  L.  Pen- 
field.     Ibid.,  vol.  46,  pp.  288-295. 

1894.  On   the   Chemical   Composition   of    Staurolite,   and  the  regular 

arrangement  of  its  Carbonaceous  Inclusions ;  by  S.  L.  Peufield 

and  J.  H.  Pratt.     Ibid.,  vol.  47,  pp.  81-89. 
On  the  Chemical  Composition  of  Chondrodite,  Humite  and  Clino- 

humite;  by  S.  L.  Penfield  and  W.  T.  H.  Howe.     Ibid.,  vol.  47, 

pp.  188-206. 
On  the  Crystallization  of  Enargite  ;  by  L.  V.  Pirsson.     Ibid.,  vol. 

47,  pp.  212-215. 

Contributions  to  the  Crystallization  of  Willemite ;  by  S.  L.  Pen- 
field.     Ibid.,  vol.  47,  pp.  305-309. 
On  the  Crystallization  of  Herderite;   by  S.  L.  Penfield.     Ibid., 

vol.  47,  pp.  329-339,  with  one  plate. 
On  the  Chemical  Composition  and   Related  Physical  Properties 


OF  MINERALOGY  AT  YALE.  19 

of  Topaz;  by  S.  L.  Penfield  and  J.  C.  Minor.    Ibid.,  vol.  47, 

pp.  387-396. 
On  Argyrodite  and  a  new  Sulphostannate  of  Silver  (Canfieldite) 

from  Bolivia  ;  by  S.  L.  Penfield.     Ibid.,  vol.  47,  pp.  451-454. 
On  Thallium  Triiodide  and  its  Relation  to  the  Alkali-Metal  Tri- 

iodides;  by  H.  L.  Wells  and  S.  L.  Penfield.     Ibid.,  vol.  47,  pp. 

463-466. 
On  some  Methods  for  the  Determination  of  Water;   by  S.   L: 

Penfield.     Ibid.,  vol.  48,  pp.  30-37. 
Mineralogical    Notes   (Octahedrite,   Penfieldite,   Oligoclase);  by 

S.  L.  Penfield.     Ibid.,  vol.  48,  pp.  114-118. 
Mineralogical   Notes   (Identity  of  Hydrofranklinite  and  Chalco- 

phanite.      On  the   Separation   of    Minerals   of    High   Specific 

Gravity)  ;  by  S.  L.  Penfield  and  D.  A.  Kreider.      Ibid.,  vol. 

48,  pp.  141-144. 
On  the  Determination  of  Ferrous  Iron  in   Silicates ;  by  J.   H. 

Pratt.     Ibid.,  vol.  48,  pp.  149-151. 
On  Hemimorphic  Wulf enite  Crystals  from  New  Mexico ;  by  C.  A. 

Ingersoll.     Ibid.,  vol.  48,  pp.  193-195. 
Mineralogical  Notes  (Cerussite,  Calamine,  Zircon) ;  by  J.  H.  Pratt. 

Ibid.,  vol.  48,  pp.  212-215. 
On  the  Occurrence  of  Leadhillite  in  Missouri  and  its  Chemical 

Composition;  by  L.  V.  Pirsson  and  H.  L.  Wells.     Ibid.,  vol. 

48,  pp.  219-226. 

1895.  On   the   Crystallization  of  the   Double   Halides  of  Caesium,   Ru- 

bidium, Sodium,  and  Lithium  with  Thallium;   by  J.  H.  Pratt. 

Ibid.,  vol.  49,  pp.  397-404. 
Calaverite  from  Cripple  Creek,  Colorado;  by  W.  F.  Hillebrand. 

With  note  on  the  Crystallization  of  Calaverite;  by  S.  L.  Pen- 
field.     Ibid.,  vol.  50,  pp.  128-131. 
Effect  of  the  Mutual   Replacement  of   Manganese  and  Iron  on 

the  Optical  Properties  of  Lithiophilite  and  Triphylite;  by  S.  L. 

Penfield  and  J.  H.  Pratt.     Ibid.,  vol.  50,  pp.  387-390. 
On  some  Devices  for  the  Separation  of  Minerals  of  High  Specific 

Gravity,  by  S.  L.  Penfield'.     Ibid.,  vol.  50,  pp.  446-448. 
Minerals  and  How  to  Study  Them  ;  by  E.  S.  Dana.     380  pp. 

1896.  On  the  Epidote  from  Huntington,  Massachusetts,  and  the  Optical 
Properties  of  Epidote;  by  E.  H.  Forbes.     Arner.  Jour.  Sci.  (4), 

vol.  1,  pp.  26-30. 

Fayalite  from  Rockport,  Massachusetts,  and  on  the  Optical  Prop- 
erties of  the  Chrysolite-Fay alite  Group  and  of  Monticellite  ;  by 
S.  L.  Penfield  and  E.  H.  Forbes.  Ibid.,  vol.  1,  pp.  129-135. 

On  the  Occurrence  of  Thaumasite  at  West  Paterson,  New  Jersey ; 
by  S.  L.  Penfield  and  J.  H.  Pratt.  Ibid.,  vol.  1,  pp.  229-233. 


20  HISTORY  AND  DEVELOPMENT 

On  the  Occurrence  of  Pollucite,  Mangano-Columbite  and  Microlite 

atRumford,  Maine;  by  H.  W.  Foote.  Ibid.,  vol.  1,  pp.  457-461. 
On  Pearceite,  a  Sulpharseirite  of  Silver,  and  on  the  Crystallization 

of  Polybasite;  by  S.  L.  Penfield.      Ibid.,  vol.  2,  pp.  17-29. 
On    Northupite;    Pirssonite,    a  new  Mineral;    Gay-Lussite   and 

Hanksite  from  Borax  Lake,  San  Bernardino  Co.,    California; 

by  J.  H.  Pratt.     Ibid.,  vol.  2,  pp.  123-135. 

1897.  On    Roeblingite,  a   new  Silicate  from   Franklin   Furnace,  New 

Jersey,  containing  Sulphur  Dioxide  and  Lead;  by  S.  L.  Pen- 
field  and  H.  W.  Foote.  Ibid.,  vol.  3,  pp.  413-415. 

On  Wellsite,  a  New  Mineral ;  by  J.  H.  Pratt  and  H.  W.  Foote. 
Ibid.,  vol.  3,  pp.  443-448. 

On  the  Identity  of  Chalcostibite  (Wolfsbergite)  and  Guejarite, 
and  on  Chalcostibite  from  Huanchaca,  Bolivia ;  by  S.  L.  Pen- 
field  and  A.  Frenzel.  Ibid.,  vol.  4,  pp.  27-35. 

On  Bixbyite,  a  new  Mineral,  and  Notes  on  the  Associated  Topaz  ; 
by  S.  L.  Penfield  and  H.  W.  Foote.  Ibid.,  vol.  4,  pp.  105-108. 

Note  Concerning  the  Composition  of  Ilmenite;  by  S.  L.  Penfield 
and  H.  W.  Foote.  Ibid.,  vol.  4,  pp.  108-110. 

On  the  Chemical  Composition  of  Hamlinite  and  its  Occurrence 
with  Bertrandite  at  Oxford  Co.,  Maine;  by  S.  L.  Penfield. 
Ibid.,  vol.  4,  pp.  313-316. 

On  the  Crystallography  of  the  Montana  Sapphires ;  by  J.  H.  Pratt. 
Ibid.,  vol.  4,  pp.  424-428. 

On  Diacyl  Analides;  H.  L.  Wheeler  and  T.  E.  Smith,  including  a 
description  of  crystalline  forms ;  by  C.  H.  Warren.  Amer. 
Chem.  Journal,  vol.  19,  pp.  757-766. 

1898.  On  Clinohedrite,  a  new  mineral  from  Franklin,  New  Jersey ;  by 

S.  L.  Penfield  and  H.  W.  Foote.     Amer.  Jour.  Sci.,  vol.  5,  pp. 

289-293. 
On  Rhodolite,  a  new  variety  of  garnet;  by  W.  E.  Hidden  and  J. 

H.  Pratt.     Ibid.,  vol.  5,  pp.  294-296. 

On  Krennerite,  from  Cripple  Creek,  Colorado;  by  A.  H.  Ches- 
ter, with  Crystallographic  Note;  by  S.  L.  Penfield.  Ibid.,  vol.  5, 

pp.  375-377. 
Mineralogical  Notes  (Melanotekite,  Kentrolite,  Pseudomorphs  after 

Phenacite  and  Topaz,  Tapiolite,  Tantalite,  Smithsonite) ;  by  C. 

H.  Warren.     Ibid.,  vol.  6,  pp.  116-124. 
Occurrence  of  Sperrylite  in  North  Carolina ;  by  W.  E.  Hidden. 

With  note  on  Crystallization  and  Chemical  Tests;  by  S.   L. 

Penfield.     Ibid.,  vol.  6,  pp.  381-383. 
Manual  of  Determinative  Mineralogy  and  Blowpipe  Analysis ;  by 

G.  J.  Brush.     Revised  and  Enlarged,  with  entirely  new  tables 

for  the  identification  of  Minerals;  by  S.  L.  Penfield.     312  pp. 


OF  MINERALOGY  AT  YALE.  21 

A  Text-Book  of  Mineralogy,  with  an  extended  Treatise  on  Crys- 
tallography and  Physical  Mineralogy ;  by  E.  S.  Dana.  593  pp. 

1899.  On  the  Chemical  Composition  of  Tourmaline ;  by  S.  L.  Penfield 

and  H.  W.  Foote.     Amer.  Jour.  Sci.,  vol.  7,  pp.  97-125. 

On  the  Chemical  Composition  of  Parisite  and  a  new  occurrence  of 
it  at  Ravalli  Co.,  Montana ;  by  S.  L.  Penfield  audC.  H.  Warren. 
Ibid.,  vol.  8,  pp.  21-24. 

On  some  new  Minerals  from  the  Zinc  Mines  at  Franklin,  New 
Jersey  (Hancockite,  Glaucochroite,  Nasonite,  Leucophoenicite) 
and  Note  concerning  the  Chemical  Composition  of  Ganomalite; 
by  S.  L.  Penfield  and  C.  H.  Warren.  Ibid.,  vol.  8,  pp.  339-353. 

First  Appendix  to  the  Sixth  Edition  of  Dana's  System  of  Min- 
eralogy ;  by  E.  S.  Dana.  75  pp. 

1900.  On  Graftonite,  a  new  Mineral  from  Grafton,  New  Hampshire,  and 

its  Intergrowth  with   Triphylite;  by   S.   L.    Penfield.     Amer. 

Jour.  Sci.,  vol.  9,  pp.  20-32. 
Siliceous  Calcites  from  the  Bad  Lands,  Washington  County,  South 

Dakota;  by  S.  L.  Penfield  and  W.  E.  Ford.     Ibid.,  vol.  9,  pp. 

352-354. 
On  the  Chemical  Composition  of  Sulphohalite ;  by  S.  L.  Penfield. 

Ibid.,  vol.  9,  pp.  425-428. 
The  Interpretation  of  Mineral  Analyses;  a  Criticism  of  recent 

Articles  on  the  Constitution  of  Tourmaline ;  by  S.  L.  Penfield. 

Ibid.,  vol.  10,  pp.  19-32. 
On  some  Interesting  Developments  of  Calcite  Crystals  ;  by  S.  L. 

Penfield  and  W.  E.  Ford.     Ibid.,  vol.  10,  pp.  237-244. 
Contactgoniometer  und  Transporteur  von  Einfacher  Construction. 

Zeitschr.  fur  Kryst.,  vol.  33,  pp.  548-554. 
On  the  Chemical  Composition  of  Turquois;  by  S.  L.  Penfield. 

Amer.  Jour.   Sci.,  vol.  10,  pp.  346-350. 

1901.  The  Stereographic  Projection  and  its  Possibilities,  from  a  graphi- 

cal Standpoint;  by  S.  L.  Penfield.     Ibid.,  vol.  11,  pp.  1-24  and 
115-144,  with  four  plates. 

SUMMARY  OF   THE   NEW  MINERAL   SPECIES  DESCRIBED 
FROM  THE  YALE  LABORATORIES. 

Beryllonite;  by  E.  S.  Dana  and  H.  L.  Wells,  1888,  1889.  A 
phosphate  of  sodium  and  beryllium,  NaBePO4,  from  Stoneham, 
Maine.  Crystallization  orthorhombic. 

Bixbyite;  by  S.  L.  Penfield  and  H.  W.  Foote,  1897.  A  combina- 
tion of  iron  and  manganese  oxides,  essentially  FeMnO3,  from 
near  Simpson,  Utah.  Crystallization  isometric,  indicating  that 
the  mineral  is  related  to  perofskite,  CaTiO8. 


22  HISTORY  AND  DEVELOPMENT 

Canfieldite  ;  by  S.  L.  Penfield,  1894.  Essentially  a  sulphostannate 
of  silver,  Ag8SnS6  =  4AgaS  .  SnS2,  with  a  little  of  the  isomorph- 
ous  germanium  molecule  Ag8GeS6,  from  Potosi,  Bolivia.  Crys- 
tallization isometric. 

Clinohedrite ;  by  S.  L.  Peufield  and  H.  W.  Foote,  1898.  A 
silicate  and  hydroxide  of  zinc  and  calcium  [ZriOH]  [CaOH] 
SiO8,  from  Franklin,  N.  J.  Crystallization  monoclinic,  clino- 
hedral  group. 

Cookeite;  by  G.  J.  Brush,  1866.  A  hydrated  silicate  of  alu- 
minium, lithium,  and  potash,  related  to  the  micas,  from  Hebron 
and  Paris,  Maine. 

Dickinsonite ;  by  G.  J.  Brush  and  E.  S.  Dana,  1878.  A  normal 
phosphate,  R3[PO4]2  .  |H20,  where  R  =  Mn,  Fe,  Ca,  Na2,  K2 
and  Li2,  from  Branchville,  Connecticut.  Crystallization  mono- 
clinic. 

Durangite;  by  G.  J.  Brush,  1869.  A  fluo-arsenate  of  aluminium, 
iron,  and  sodium,  Na[AlF]AsO4,  with  some  Fe  isomorphous 
with  Al,  from  Durango,  Mexico.  Crystallization  monoclinic. 

Durdenite  ;  by  E.  S.  Dana  and  H.  L.  Wells,  1890..  A  tellurite  of 
ferric  iron,  Fe2[Te08]3  .  4H2O,  from  the  Ojojoma  District, 
Honduras. 

Eosphorite;  by  G.  J.  Brush  and  E.  S.  Dana,  1878.  A  hydrated 
phosphate  of  aluminium  and  manganese  [AlO]MnPO4  .  2H2O, 
with  a  little  Fe  isomorphous  with  Mn,  from  Branchville,  Con- 
necticut. The  mineral  is  related  to  childrenite  [AlO]FePO4  . 
2H2O.  Crystallization  orthorhombic. 

Eucryptite;  by  G.  J.  Brush  and  E.  S.  Dana,  1880.  An  ortho- 
silicate  of  aluminium  and  lithium,  LiAlSi()4,  resulting  from  the 
alteration  of  spodumene,  from  Branchville,  Connecticut.  Crys- 
tallization hexagonal. 

Fairfieldite ;  by  G.  J.  Brush  and  E.  S.  Dana,  1879.  A  hydrated 
phosphate,  R3[PO4]2  .  2H2O,  where  R  =  Ca,  Mn,  and  Fe,  from 
Branchville,  Connecticut.  Crystallization  triclinic. 

Fillowite;  by  G.  J.  Brush  and  E.  S.  Dana,  1879.  A  hydrated 
phosphate,  R8[PO4]2  .  £H2O,  where  R  =  Mn,  Fe,  Ca,  and  Na2, 
from  Branchville,  Connecticut.  Crystallization  monoclinic. 

Gerhardtite ;  by  H.  L.  Wells  and  S.  L.  Penfield,  1885.  A  basic 
nitrate  of  copper,  [CuOH]NO3  .  Cu[OH]2,  from  Jerome,  Ari- 
zona. Crystallization  orthorhombic. 

Glaucochroite  ;  by  S.  L.  Penfield  and  C.  H.  Warren,  1899.  An 
orthosilicate  of  calcium  and  manganese,  CaMnSiO4,  from  Frank- 
lin, New  Jersey.  Glaucochroite  is  related  to  monticellite, 
CaMnSiO4.  Crystallization  orthorhombic. 

Graftonite  ;    by    S.   L.   Penfield,   1900.      A    normal    phosphate 


OF  MINERALOGY  AT  YALE.  23 

R3[PO4]2,  R  =  Fe,  Mn,  and  Ca,  from  Graf  ton,  New  Hampshire. 
Crystallization  monoclinic.  The  material  is  curiously  inter- 
grown  with  triphylite. 

Hamlinite ;  by  W.  E.  Hidden  and  S.  L.  Penfield,  1890.  A  phos- 
phate, occurring  very  sparingly  with  herderite  at  Stoneham, 
Maine.  Crystallization  hexagonal,  rhombohedral. 

Hancockite;  by  S.  L.  Penfield  and  C.  H.  Warren,  1899.  A 
silicate  related  to  epidote  and  piedmontite,  but  containing  a 
considerable  quantity  of  lead,  from  Franklin,  New  Jersey. 
Crystallization  monoclinic. 

Hortonolite;  by  G.  J.  Brush,  1869.  An  orthosilicate,  R2Si04, 
where  R  =  Fe,  Mn,  and  Mg,  from  Monroe,  New  York.  Hortono- 
lite is  related  to  f ayalite,  and  is  intermediate  between  f ayalite 
and  chrysolite.  Crystallization  orthorhombic. 

Jefferisite  ;  by  G.  J.  Brush,  1866.  A  hydrated  micaceous  min- 
eral belonging  to  the  vermiculite  group,  from  Westchester, 
Pennsylvania. 

Leucophcenicite ;  by  S.  L.  Penfield  and  C.  H.  Warren,  1899.  A 
manganese  silicate,  Mn5[MnOH]2[SiO4]8,  with  a  little  Zn  and 
Ca  isomorphous  with  the  Mn,  from  Franklin,  New  Jersey. 
Leucophcenicite  is  equivalent  to  a  manganese  humite. 

Lithiophilite;  by  G.  J.  Brush  and  E.  S.  Dana,  1878.  Essentially 
LiMnPO4,  with  a  little  Fe  isomorphous  with  Mu,  from  Branch- 
ville,  Connecticut.  Lithiophilite  is  related  to  triphylite,  LiFePO4. 
Crystallization  orthorhombic. 

Nasonite ;  by  S.  L.  Penfield  and  C.  H.  Warren,  1899.  A  meso- 
silicate,  Pb4[PbCl]2Ca4[Si2O7]3,  from  Franklin,  New  Jersey. 
Nasonite  is  related  to  ganomalite,  Pb4[PbOH]2Ca4[Si2O7]8. 
Crystallization  tetragonal. 

Natrophilite  ;  by  G.  J.  Brush  and  E.  S.  Dana,  1890.  Essentially 
NaMnPO4,  with  some  Fe  isomorphous  with  Mn,  from  Branch- 
ville,  Connecticut.  Crystallization  orthorhombic. 

Nesquehonite ;  by  F.  A.  Genth  and  S.  L.  Penfield,  1890.  A  hy- 
drated magnesium  carbonate  MgCO8  .  3H2O,  from  Nesquehonig, 
Schuylkill  Co.,  Pennsylvania.  Crystallization  orthorhombic. 

Pearceite  ;  by  S.  L.  Penfield,  1896.  Essentially  Ag9AsS6,  equi- 
valent to  an  arsenical  polybasite,  from  Marysvale,  Lewis  and 
Clarke  Co.,  Montana.  Crystallization  monoclinic. 

Pirssonite ;  by  J.  H.  Pratt,  1896.  A  hydrated  carbonate  of  sodium 
and  calcium,  Na2CO8  .  CaCO3  .  2H2O,  from  San  Bernardino  Co., 
California.  Crystallization  orthorhombic,  hemimorphic. 

Ralstonite;  by  G.  J.  Brush,  1871.  A  hydrous  fluoride  of  alumin- 
ium, sodium,  and  magnesium,  from  Arksuk-nord,  West  Green- 
land. Crystallization  isometric. 


24  HISTORY  AND  DEVELOPMENT 

Reddingite;  by  G.  J.  Brush  and  E.  S.  Dana,  1878.  A  normal 
phosphate,  Mn8[PO4]2  .  3H2O,  with  Fe  isomorphous  with  Mn, 
from  Branchville,  Connecticut.  Crystallization  orthorhombic. 

Roeblingite ;  by  S.  L.  Penfield  and  H.  W.  Foote,  1897.  A  com- 
plex silicate  of  calcium  and  lead  containing  a  sulphite  radical, 
H10Ca7Pb2Si5S2O28,  from  Franklin,  New  Jersey. 

Selen-tellurium ;  by  E.  S.  Dana  and  H.  L.  Wells,  1890.  A 
combination  of  selenium  and  tellurium  from  Tegucigalpa, 
Honduras. 

Spangolite ;  by  S.  L.  Penfield,  1890.  A  hydrated  sulphate  and 
chloride  of  copper  and  aluminium  [A1C1]SO4  .  6Cu(OH)2  .  3H2O, 
from  near  Tombstone,  Arizona.  Crystallization  hexagonal- 
rhombohedral,  hemimorphic. 

Sperrylite;  by  H.  L.  Wells,  1889.  Arsenide  of  platinum,  PtAs2, 
from  the  district  of  Algoma,  Ontario,  Canada.  Crystallization 
isome  tric-py  ritohedral . 

Sussexite;  by  G.  J.  Brush,  1868.  A  borate,  HRBO3,  where 
R  =  Mn,  Mg,  and  a  little  Zn,  from  Franklin,  New  Jersey. 

Triploidite  ;  by  G.  J.  Brush  and  E.  S.  Dana,  1878.  A  phosphate, 
R[ROH]PO4,  where  R  =  Mn  and  Fe,  from  Branchville,  Connec- 
ticut. Crystallization  monoclinic.  Triploidite  is  closely  related 
to  triplite,  R[RF]PO4,  where  R  =  Mn  and  Fe,  and  to  wagnerite, 
Mg[MgF]PO4,  and  its  discovery  was  of  especial  importance  as  it 
illustrated  in  a  simple  and  striking  manner  the  isomorphous 
relations  of  hydroxyl  and  fluorine  in  the  radicals  [ROH]  and 
[RF]. 

Tysonite ;  by  O.  D.  Allen  and  W.  J.  Comstock,  1880.  A  fluoride 
of  the  rare-earth  metals,  [Ce,La,Di]F3,  from  Pike's  Peak,  Col- 
orado. Crystallization  hexagonal. 

Wellsite;  by  J.  H.  Pratt  and  H.  W.  Foote,  1897.  A  silicate 
R Al2Si3O10 .  3H2O,  where  R  =  Ca,  Ba,  Sr,  Na2  and  K2,  from  Buck 
Creek,  Clay  Co.,  North  Carolina.  Crystallization  monoclinic, 
Wellsite  is  closely  related  to  harmotome  and  phillipsite. 

SUMMARY  OF  MINERALS  WHOSE  FORMULAS  HAVE  BEEN 
DETERMINED  IN  THE  YALE  LABORATORIES,  EXCLUSIVE  OF 
THOSE  GIVEN  IN  THE  PREVIOUS  LIST  OF  NEW  MINERALS. 

Alunite,  R[A1(OH)2]3[SO4]2,  R  =  K  and  Na.  This  comparatively 
simple  formula  was  derived  from  an  analysis  of  alunite  from 
Red  Mountain,  Colorado,  by  E.  B.  Hurlburt,  1893.  It  was 
shown  that  the  mineral  contains  hydroxyl  and  not  water  of 
crystallization. 

Alurgite,   HR2[A10H]Al[Si03]4,   R  =  K  and   (MgOH).      The 


OF  MINERALOGY  AT  YALE.  25 

mineral  belongs  to  the  mica  group,  and  the  formula  was 
derived  from  an  analysis  by  S.  L.  Penfield,  1893,  of  a  specimen 
from  Piedmont,  Italy. 

Amblygonite,  Li[AlF]PO4  and  Li[AlOH]PO4.  Analyses  of  eight 
varieties  of  the  mineral  from  different  localities  by  S.  L.  Pen- 
field,  1879,  indicate  that  the  composition  may  be  regarded  as 
mixtures,  in  varying  proportions,  of  the  foregoing  isomorphous 
fluorine  and  hydroxyl  molecules. 

Argyrodite,  Ag8GeS6  =  4Ag2S  .  GeS2.  Analyses  of  specimens 
from  Bolivia  and  Saxony  by  S.  L.  Penfield,  1893,  indicate  the 
foregoing  composition  and  not  3Ag2S  .  GeS2,  as  determined  by 
another  investigator. 

Aurichalcite,  2RC08  .  3R[OH]2,  R  =  Zn  and  Cu.  The  formula 
was  derived  from  two  analyses  by  S.  L.  Penfield,  1891,  of  very 
pure  material  from  unknown  localities  in  Utah. 

Childrenite,  Fe[AlO]PO4  .  2H2O,  a  little  Mn  and  Ca  isomor- 
phous with  Fe.  The  formula  was  derived  from  an  analysis  of 
material  from  Tavistock,  Wales,  by  S.  L.  Penfield,  1879.  The 
formula  was  thus  shown  to  be  analogous  to  that  of  eosphorite 
Mn[AlO]PO4  .  2H2O.  Water  is  all  expelled  at  a  low  tempera- 
ture ;  hence  the  mineral  contains  no  hydroxyl. 

Chondrodite,  and  the  minerals  of  t'he  chondrodite  group,  humite 
and  cliriohumite.  From  analyses  of  four  specimens  of  chon- 
drodite, two  of  humite  and  two  of  clinohumite  by  S.  L.  Penfield 
and  W.  T.  H.  Howe,  189i,  it  was  shown  that  the  minerals  of 
this  group  form  a  series  differing  from  one  another  by  a  mole- 
cule of  Mg0SiO4  as  follows  : 

Chondrodite  Mg8[Mg(F,OH)]2[SiO4]2 

Humite  Mg6[Mg(F,OH)]2[SiO4]8 

Clinohumite  Mg7[Mg(F,OH)]2[SiO4]4. 

In  the  radical  [Mg(F,OH)]  fluorine  and  hydroxyl  are  regarded 
as  isomorphous. 

Clinohumite,  Mg7[Mg(F,OH)]2[SiO4]4,  see  Chondrodite. 

Connellite,  Cu15[Cl,OH]4SO16  .  15H2O.  The  formula  of  this 
basic  combination  of  a  sulphate  and  chloride  of  copper  was 
derived  from  an  analysis  by  S.  L.  Penfield,  1890,  made  on 
0.0740  grams  of  the  exceedingly  rare  material  from  Cornwall, 
England. 

Cookeite,  Li[Al(OH)2]3[SiO3]2.  Formula  derived  from  an  analysis 
by  S.  L.  Penfield,  1893,  of  material  from  Paris,  Maine. 

Ganomalite,  Pb4[PbOH]2Ca4[Si2O7]3.  This  formula  is  made  prob- 
able by  the  investigation  of  the  new  mineral  Nasonite,  the 
corresponding  chlorine  compound,  Pb4[PbCl]2Ca4[Si2O7]3,  by 
S.  L.  Penfield  and  C.  H.  Warren,  1899. 


26  HISTORY  AND  DEVELOPMENT 

Hamlinite,  [Al(OH)2]3[Sr(OH)]P2O7,  with  some  Ba  isomorphous 
with  Sr.  The  formula  was  derived  from  an  analysis  by  S.  L. 
Penfield,  1897,  of  material  from  Oxford  Co.,  Maine. 

Hanksite,  9Na2SO4  .  2Na2CO8  .  KC1.  This  complex  formula, 
containing  three  acid  radicals,  is  derived  from  an  analysis  by 
S.  L.  Penfield,  1885,  and  two  analyses  by  J.  H.  Pratt,  1896,  on 
entirely  different  samples  of  material  from  San  Bernardino  Co., 
California. 

Herderite,  Ca[Be(F,OH)]PO4.  The  formula  indicating  the  iso- 
morphous relations  of  the  radicals  [BeF]  and  [BeOH]  was 
established  by  an  analysis  of  the  mineral  from  Stoneham,  Maine, 
by  S.  L.  Penfield  and  D.  N.  Harper,  1886. 

Howlite,  H5Ca2B5SiO14.     This  formula  was  derived  from  an  analy- 
sis by  S.  L.  Penfield  and  E.  S.  Sperry,  1887,  of  exceptionally 
pure  material  from  Windsor,  Nova  Scotia.     The  analysis  served 
to  give  howlite  the  rank  of  a  well  defined  mineral  species. 
'  Humite,  Mg5[Mg(F,OH)]2[SiO4]3,see  Chondrodite. 

Hydro-herderite  Ca[BeOH]PO4.  The  existence  of  a  variety  of 
herderite  free  from  fluorine  was  established  by  an  analysis  by 
H.  L.  Wells,  1892,  of  a  specimen  from  Hebron,  Maine. 

Ilinenite,  RO  .  TiO2,  where  R  =  Fe  and  Mg.  That  ilmenite  is 
a  combination  of  FeO  and  TiO2,  in  other  words  a  titanate  of 
iron,  and  not  an  isomorphous  mixture  of  Fe2O3  and  Ti2O8,  is 
shown  by  an  analysis  by  H.  W.  Foote,  1897,  of  crystallized 
ilmenite  from  Orange  Co.,  New  York,  containing  a  large  propor- 
tion of  MgO.  The  presence  of  MgO  in  the  mineral  indicates 
that  the  iron  must  exist  in  the  ferrous  condition  as  FeO,  with 
which  MgO  is  isomorphous. 

lolite,  [Mg,  Fe]4Al8[OH]2[Si2O7]5.  Two  analyses  of  exceptionally 
pure  material  by  O.  H.  Farrington,  1892,  served  to  establish  the 
foregoing  formula. 

Jarosite  K[Fe(OH)2]3[SO4]2.  This  formula  follows  as  a  result  of 
the  investigation  of  the  isomorphous  compound  Alunite  by  E.  B. 
Hurlburt,  page  24. 

Kentrolite,  [Mn4O3]  Pb3[Si04]8.  This  formula  follows  as  a  result 
of  the  investigation  of  the  isomorphous  compound  Melanotekite 
by  C.  H.  Warren. 

Leadhillite,  Pb2[PbOH]2[SO4][CO8]2.  Formula  established  by 
an  analysis  by  H.  L.  Wells,  1894,  of  very  pure  material  from 
Granby,  Missouri. 

Melanotekite,  [Fe4O3]Pb8[SiO4]8.  Formula  established  by  an 
analysis  by  C.  H.  Warren,  1898,  of  material  from  Hillsboro, 
New  Mexico.  The  formula  of  the  isomorphous  mineral  ken- 
trolite  was  shown  to  be  [Mn4O8]Pb8[SiO4]  as  a  result  of  this 
investigation. 


OF  MINERALOGY  AT  YALE.  27 


Monazite,  [Ce,La,Di]PO4,  with  admixture  of  ThSiO4.  The  pres- 
ence of  the  molecule  ThSiO4  was  shown  by  three  analyses 
by  S.  L.  Penfield,  1882,  and  a  later  analysis  by  S.  L.  Penfield 
and  E.  S.  Sperry,  1888.  It  was  pointed  out  in  the  original  in- 
vestigation that  ThSiO4  was  present  in  monazite  as  an  impurity, 
but  it  seems  more  probable  from  later  considerations  that  ThSiO4 
crystallizes  with  CePO4  as  an  isomorphous  constituent. 

Mordenite,  [Ca,Na2K2]Al2Si9O22 .  6H2O.  Derived  by  L.  V.  Pirsson, 
1890,  from  an  analysis  of  material  from  the  Yellowstone  National 
Park. 

Northupite,  MgCO8,  Na2CO3,  NaCl.  Formula  established  by  J. 
H.  Pratt,  1896,  from  an  analysis  of  crystals  from  San  Bern- 
ardino Co.,  California. 

Parisite,  [RF]2Ca[CO3]8,  where  R  =  Ce,La,  and  Di.  Formula  estab- 
lished by  two  analyses  by  C.  H.  Warren,  1899,  on  crystallized 
material  from  RavalliCo.,  Montana,  and  Muso,  U.  S.  Colombia. 

Pollucite,  H2Cs4Al4[SiO3]9.  Derived  from  analyses  by  H.  L. 
Wells,  1891,  of  material  from  Hebron,  Maine. 

Ralstonite,  [Mg,Na2]Al3[F,OH]n  .  2H2O.  An  analysis  by  S.  L. 
Penfield  and  D.  N.  Harper,  1886,  indicates  that  the  mineral 
contains  both  water  of  crystallization  and  hydroxyl.  The 
hydroxyl  when  taken  as  isomorphous  with  the  fluorine  leads 
to  the  foregoing  formula. 

Spodumene,  LiAl[SiO8]2,  with  a  little  Na  isomorphous  with  Li. 
The  foregoing  simple  formula  was  derived  by  G.  J.  Brush,  1850, 
from  two  analyses  of  the  mineral  from  Norwich  and  Sterling, 
Massachusetts.  It  was  subsequently  shown  by  Rarnmelsberg 
that  the  mineral  had  a  far  more  complicated  composition,  and 
it  was  not  until  1878  that,  as  a  result  of  a  reinvestigation  of  the 
mineral  by  Doelter,  the  simple  composition  derived  by  Professor 
Brush  was  re-established. 

Staurolite,  [AlO]4[AlOH]Fe[Si04]2,  with  Mg  isomorphous  with 
Fe.  The  foregoing  formula  was  derived  from  four  analyses  by 
S.  L.  Penfield  and  J.  H.  Pratt,  1894,  of  carefully  purified 
materials. 

Sulphohalite,  2Na2SO4,  NaCl,  NaF.  Derived  from  an  analysis  by 
S.  L.  Penfield,  1900,  of  the  exceedingly  rare  material  from  San 
Bernardino  Co..  California.  The  formula  is  interesting  as 
indicating  the  existence  of  three  acid  constituents  in  a  single 
compound. 

Topaz,  [AlF]2SiO4  with  admixture  of  the  isomorphous  hydroxyl 
compound  [A10H]2SiO4.  The  existence  of  the  hydroxyl  mole- 
cule was  shown  by  analyses  of  six  varieties  of  topaz  by  S.  L. 
Penfield  and  J.  C.  Minor,  1894.  The  optical  properties  of 


28  HISTORY  AND  DEVELOPMENT 

topaz,  which  had  previously  been  regarded  as  anomalous,  were 
shown  to  be  dependent  upon  the  presence  of  the  hydroxyl  mole- 
cule in  greater  or  less  amount. 

Tourmaline,  H9Al8B2[OH]2Si4O19,  the  nine  hydrogen  atoms  being 
replaced  in  varying  amounts  by  metals  of  varying  valence,  Al, 
Fe,  Mn,  Mg,  Ca,  Na,  K,  Li.  Fluorine  replaces  part  of  the 
hydroxyl.  The  empirical  formula  of  the  tourmaline  acid, 
H18B2[OH]2Si4O19,  was  established  by  two  analyses  of  most 
carefully  selected  materials,  by  S.  L.  Penfield  and  H.  W.  Foote, 
1899,  and  it  was  shown  that  the  many  excellent  analyses  of 
other  investigators  yield  the  same  result. 

Turquois,  [A1(OH)2,  Fe(OH)2,  Cu(OH),  H]3PO4,  in  part  [A1(OH)2, 
Fe(OH)2,  Cu(OH)]2HPO4.  Turquois  seems  to  be  a  derivative 
of  normal  phosphoric  acid,  H8PO4,  in  which  the  hydrogen 
atoms  are  replaced  in  part  by  the  univalent  radicals  [A1(OH)2], 
[Fe(OH)2]  and  [Cu(OH)].  The  formula  was  derived  by  S.  L. 
Penfield,  1900,  from  ail  analysis  of  turquois  from  Lincoln  Co., 
Nevada. 

SUMMARY  OF  MINERALS  WHOSE  CRYSTALLIZATION  HAS 
BEEN  ESTABLISHED  IN  THE  YALE  LABORATORIES,  EXCLU- 
SIVE OF  THOSE  GIVEN  IN  THE  PREVIOUS  LIST  OF  NEW 
MINERALS. 

Amarantite  :  —  Crystallization  triclinic.     Axial  ratio  determined 

and  forms  described.     S.  L.  Penfield,  1890. 
Argyrodite :  —  Crystallization    determined  to    be   isometric   and 

not  monoclinic  as  formerly  supposed.     S.  L.   Penfield,   1893. 
Bertrandite :  —  The   hemimorphic  character  of    the  species  was 

established  by  the  study  of  crystals   from  Stoneham,  Maine, 

and  Mt.  Antero,  Colorado.     S.  L.  Penfield,  1888. 
Danburite :  —  Crystallization   established   as    orthorhombic,  axial 

ratio  determined  and  forms  described.     G.  J.  Brush  and  E.  S. 

Dana,  1880. 
Herderite  :  —  Crystallization  monoclinic.     It  was  shown  that  the 

orthorhombic  habit  which  the  mineral  generally  exhibits  results 

from  twinning.     S.  L.  Penfield,  1894. 
Lansfordite  :  —  Crystallization   triclinic  ;   axial  ratio   established 

and  forms  described.     S.  L.  Penfield,  1890. 
Metacinnabarite  :  —  Crystallization  isometric  and  tetrahedral,  thus 

indicating  that  the  mineral,  HgS,  belongs  in  the  same  group 

with  sphalerite,  ZnS.     S.  L.  Penfield,  1885. 
Mordenite:  —  Crystallization  monoclinic.     Axial  ratio  established 

and  forms  described  by  L.  V.  Pirsson,  1890. 


OF  MINERALOGY  AT  YALE.  29 

Penfieldite:  —  Crystallization  established  as  hexagonal,  and  axial 
ratio  determined.  S.  L.  Penfield,  1894. 

Polianite  :  —  Crystallization  tetragonal.  Axial  ratio  determined 
and  forms  described.  It  was  shown  that  the  mineral,  MnO9, 
crystallizes  like  cassiterite  and  rutile,  SnO2  and  TiO2  respec- 
tively, and  belongs  in  the  same  group  with  them.  E.  S.  Dana 
and  S.  L.  Penfield,  1888. 

Polybasite  :  —  Crystallization  monoclinic.  Axial  ratio  determined 
and  forms  described.  The  article  includes  a  discussion  of  the 
similarity  in  crystalline  form  between  chalcocite,  Cu2S,  and  a 
number  of  sulphantimonites  and  sulpharsenites  in  which  Cu2S 
or  its  isomorphous  equivalent,  Ag2S,  predominates.  S.  L.  Pen- 
field,  1896. 

Sperrylite :  —  Crystallization  isometric  and  pyritohedral,  thus 
showing  that  the  mineral,  PtAs2,  is  analogous  to  pyrite,  FeS2. 
S.  L.  Penfield,  1889. 

Tiemannite :  —  Crystallization  isometric  and  tetrahedral,  thus 
indicating  that  the  mineral,  HgSe,  belongs  in  the  same  group 
with  sphalerite,  ZnS.  S.  L.  Penfield,  1885. 

Willemite  :  —  An  examination  of  crystals  from  the  Merritt  Mine, 
New  Mexico,  and  Franklin,  New  Jersey,'  showed  the  existence  of 
rhombohedrons  of  three  orders,  thus  indicating  that  willemite, 
Zn2SiO4,  crystallizes  like  phenacite,  Be2SiO4,  in  the  tri-rhom- 
bohedral  division  of  the  hexagonal  system.  S.  L.  Penfield, 
1894. 

The  foregoing  list  refers  only  to  minerals,  and  does  not 
include  the  determination  of  the  crystallization  of  a  large 
number  of  chemical  substances,  especially  series  of  new  double 
salts  made  in  the  Sheffield  Chemical  Laboratory.  A  list  of 
these  contributions  to  crystallography  by  S.  L.  Penfield,  H.  L. 
Wheeler,  J.  H.  Pratt,  H.  W.  Foote  and  C.  H.  Warren  may 
be  found  in  the  Bibliography  between  the  years  1892  and 
1897. 


ON  AMERICAN  SPODUMENE. 

BY   GEORGE  J.  BRUSH, 
Of  the  Yale  Analytical  Laboratory.* 

(From  Amer.  Jour.  Sci.,  1850,  vol.  10,  pp.  370-371.) 

Read  before  the  American  Association  for  the  Advancement  of  Science  at 
New  Haven,  August,   1850. 

OWING  to  the  want  of  a  complete  analysis  of  an  American 
Spodumene,  I  was  induced,  at  the  suggestion  of  Prof.  Silli- 
man,  Jr.,  to  undertake  this  research. 

The  Spodumene  from  Uto  has  often  been  the  subject  of 
chemical  investigation  and  has  been  analyzed  by  Arfvedson,f 
Stromeyer,J  Regnault,§  and  Hagen.||  That  from  the  Killiney 
locality  has  been  analyzed  by  Thomson.^]" 

These  are  all  the  complete  analyses  recorded  of  this  species ; 
partial  analyses,  however,  exist  of  specimens  from  the  Tyrol 
mountains,  and  from  Sterling,  Mass.,  the  former  by  Hagen 
and  the  latter  by  both  Hagen  and  Bo  wen. 

The  constitution  of  this  mineral  was  not  correctly  under- 
stood prior  to  Hagen's  analysis,  until  which  time  it  had  been 

*  This  may  be  considered  as  the  first  publication  by  Professor  Brush, 
although  two  analyses  made  by  him,  one  of  albite  and  the  other  of  anorthite, 
had  previously  been  published  in  a  paper  by  Professor  Silliman,  Jr.  (Amer. 
Jour.  Sci.,  1849,  vol.  8,  pp.  390-391).  It  is  interesting  to  note  that  the  oxygen 
ratio  1:3:8  derived  from  the  analyses  of  spodumene  led  to  the  simple  for- 
mula R2Al2Si4012,  R2  being  Li2,  Na2,  and  Ca.  Considering  R2  wholly  as  Li2, 
which  is  the  essential  alkali  metal,  the  formula  may  be  further  simplified  to 
LiAlSi206.  The  simple  formula  derived  by  Professor  Brush  was  questioned 
by  Rammelsberg  (Pogg.  Ann.,  vol.  85,  p.  544),  and  for  a  long  time  a  more 
complicated  composition  was  generally  assigned  to  the  mineral,  until  in  1878 
the  simple  and  correct  formula,  determined  by  Professor  Brush,  was  re- 
established by  Dcelter  (Tschermak  Min.  u,  Petr.  Mitth.,  vol.  1,  p.  517). 

t  Schweigger's  Jour.,  xxii,  107.  J  Untersuchungen,  i,  426. 

§  Ann.  des  Mines  (III.  series),  1839,  580.          ||  Pogg.  Ann.,  xlviii,  371. 
IT  Thorn.  Min.,  i,  302. 


Silica  .... 

66.136    = 

Oxygen. 

34.36 

34.36 

Alumina  .  .  . 
Peroxide  of  iron 

27.024    = 
00.321    = 

12.63  1 
0.09) 

12.72 

Lithia  .  .  . 
Soda  .... 

3.836    = 
2.683    = 

2.11  1 
0.68  j 

2.79 

ON  AMERICAN  SPODUMENE.  31 

considered  as  essentially  a  silicate  of  alumina  and  lithia. 
Hagen,  however,  found  a  portion  of  the  so-called  lithia  to  be 
soda,  which  discovery  being  confirmed  renders  the  formulas 
derived  from  former  analyses  incorrect,  owing  to  the  great 
difference  in  the  atomic  weights  of  lithia  and  soda.  Hagen's 
analysis  of  a  specimen  from  the  Uto  locality  gave 

Ratio. 

12.26        12 
4.55          4J- 

1.00          1 

=          U.OO  ) 

100.00 
from  which  he  deduced  the  formula 

NaO  .  Si03  +  3LiO  .  Si03  +  6Al203[Si03]3* 

My  analyses  agree  with  Hagen's  in  the  soda,  but  lead  to  a 
different  formula.  The  specimens  selected  for  analysis  were 
from  the  Norwich  and  Sterling  (Mass.)  localities.  A  quali- 
tative examination  of  each  showed  the  presence  of  silica, 
alumina,  peroxide  of  iron  (trace),  lime,  lithia,  and  soda. 

In  the  quantitative  examination  the  alkalies  were  obtained 
by  decomposition  by  hydrofluoric  acid  and  determined  as 
sulphates;  the  other  constituents  were  obtained  by  fusion 
with  carbonate  of  soda.  That  from  Norwich  in  two  analyses 
yielded 

II.  Mean.  Oxygen.  Ratio. 


Silica     .     63.06 

62.72 

62.89 

32.67 

32.67 

8.04 

Alumina    28.00 

28.85 

28'.42 

13.28 

13.28 

3.27 

Lime      .     00.95 

1.13 

•    1.04 

0.29) 

Lithia   .      5.67 

5.67 

5.67 

3.12V- 

4.06 

1.00 

Soda      .      2.51 

2.51 

2.51 

0.65) 

100.19 

100.88 

*  The  old  method  of  notation  is  here  employed,  the  oxides  of  sodium, 
lithium,  and  silicon  being  regarded  as  NaO,  LiO,  and  Si03,  respectively. 
—  EDITOR. 


32  ON  AMERICAN  SPODUMENE. 

And    that    from   the   Sterling  locality,   of  which   also   two 
analyses  were  made,  gave 

I.  II.  Mean.  Oxygen.  Ratio. 

Silica     .     62.86  62.67  62.76  32.61            32.61       7.80 

Alumina    28.83  29.83  29.33  13.75            13.75       3.28 

Lime     .     00.56  00.71  00.63  0.18) 

Lithia   .      6.48  6.48  6.48  3.56  C           4.19       1.00 

Soda      .      1.76  1.76  1.76  0.45 ) 

100.49  101.45 

The  mean  of  the  ratios  calculated  from  the  four  analyses 
is  1:  3.27:  7.92  or  quite  nearly  1 :  3 :  8,  which  gives  the 
general  formula 


[KO]3[Si08]2  +  3[Al203][Si03] 


* 


2 
And  the  special  formula 

[0.0570CaO  +  0.1333NaO  +  0.8097LiO]3[Si03]2  + 

3[Al203][Si03]2 
which  requires, 

Per  cent. 

8                  atoms  of  silica             4618.48  64.14 

3                 atoms  of  alumina        1925.40  26.76 

2.4291         atoms  of  lithia              441.27  6.12 

0.3999         atoms  of  soda                154.84  2.15 

0.171           atoms  of  lime                  60.10  0.83 

7200.09  =      100.00 

This  formula  corresponds  quite  well  with  the  analyses, 
especially  in  the  protoxide  bases,  the  mean  of  which  is  almost 
precisely  that  required  by  the  formula. 

*  According  to  the  present  system  of  notation  this  formula  becomes 
3R2  0  .  3A12O3  .  12Si02  =  RAlSi206. 


ON  SUSSEXITE,  A  NEW  BORATE  FROM  MINE 
HILL,  FRANKLIN  FURNACE,  SUSSEX  CO., 
NEW  JERSEY. 

BY  GEORGE  J.  BRUSH. 
(From  Am.  Jour.  Sci.,  1868,  vol.  46,  pp.  240-243.) 

IN  examining  a  specimen  of  a  fibrous  mineral,  obtained  at 
Mine  Hill  last  year,  I  found  that  it  was  a  fibrous  silicate  of 
zinc,  and  being  desirous  of  further  investigating  the  mineral, 
I  requested  my  assistant,  Mr.  Wm.  G.  Mixter,  on  his  recent 
visit  to  the  locality,  to  obtain  as  much  of  the  fibrous  sub- 
stance as  possible,  so  that  a  quantitative  analysis  might  be 
made  of  it.  Mr.  Mixter  was  fortunate  in  obtaining  one  speci- 
men of  what  we  at  first  sight  took  to  be  the  fibrous  silicate, 
but  on  examination  of  its  pyrognostic  characters  it  proved  to 
be  a  new  mineral,  a  hydrous  fusible  borate,  reacting  strongly 
with  the  fluxes  for  manganese.  This  interesting  discovery 
led  me  at  once  to  revisit  the  locality,  and  I  there  succeeded 
in  obtaining  enough  of  the  new  mineral  to  give  the  following 
characters.  It  is  found  in  the  franklinite  vein  at  the  opening 
on  the  north  end  of  Mine  Hill,  associated  with  franklinite, 
zincite,  willemite,  tephroite,  calcite  and  what  appears  to  be 
a  double  carbonate  of  manganese  and  magnesia  occurring 
implanted  on,  or  imbedded  in  the  fibrous  mineral  in  minute 
hemispherical  forms;  it  has  also,  associated  with  it,  a  black 
hydrate  of  manganese,  apparently  the  species  manganite,  and 
a  pale  pink  carbonate  which  is  probably  rhodochrosite.  The 
black  manganite  and  the  double  carbonate  have  the  appear- 
ance of  being  products  of  the  alteration  of  the  borate,  since, 
where  associated  with  these,  the  latter  seems  exceedingly 
friable  and  evidently  in  process  of  decomposition. 

The  pure  mineral  is  whitish  with  a  tinge  of  yellow  or  pink? 
is  translucent  on  the  edges  and  in  thin  fragments,  and  pos- 


34  OAT  SUSSEXITE,   A   NEW  BORATE 

sesses  a  silky  to  pearly  luster.  The  structure  is  fibrous, 
sometimes  asbestiform,  although  in  other  specimens  it  seems 
to  cleave  much  more  readily  in  one  direction  than  in  a  direc- 
tion at  right  angles  to  this,  yielding  flat  fibrous  fragments. 
The  mineral  occurs  in  seams  in  calcite,  sometimes  with  the 
fibers  running  transversely,  and  in  other  specimens  quite  long 
and  parallel  to  the  seam.  The  hardness  is  slightly  above  3, 
scratching  calcite,  but  not  aragonite.  Specific  gravity  —  3.42. 

On  heating  in  the  closed  tube  the  mineral  darkens  slightly 
in  color  and  yields  water  which  reacts  neutral  to  test-papers ; 
but  if  turmeric  paper  is  moistened  with  this  water,  then  with 
a  drop  of  dilute  chlorhydric  acid  and  afterwards  dried,  it 
assumes  the  red  color  characteristic  of  boric  acid,  and  thus 
shows  that  at  least  a  trace  of  this  acid  is  driven  off  with  the 
water.  In  the  forceps  the  mineral  fuses  in  the  flame  of  a 
candle  (F.  =  2)  and  B.  B.  in  O.  F.  yields  a  black  crystalline 
mass  and  colors  the  flame  intensely  yellowish-green.  With 
borax  and  salt  of  phosphorus  it  gives  a  deep  amethystine  bead 
in  O.  F.,  which  in  R.  F.  becomes  colorless  and  transparent. 
With  soda  it  yields  a  green  manganate. 

It  is  readily  dissolved  in  chlorhydric  acid,  and  most  speci- 
mens thus  treated  give  off  a  minute  quantity  of  chlorine, 
showing  traces  of  a  slight  alteration  of  the  protoxide  of  man- 
ganese into  a  higher  oxide.  On  evaporation  to  dryness  and 
resolution  in  acid,  minute  imponderable  traces  of  silica  were 
found.  Qualitative  analysis  proved  the  presence  of  boric 
acid,  manganese,  magnesia,  and  water,  with  questionable 
traces  of  zinc  and  soda.  A  fragment  of  the  mineral  moist- 
ened with  sulphuric  acid  and  held  in  the  flame  of  an  ordinary 
Bunsen  burner  gave,  when  observed  through  the  spectroscope, 
the  characteristic  spectrum  of  boric  acid. 

The  exceedingly  simple  composition  of  the  mineral  rendered 
the  quantitative  determination  of  the  bases  comparatively 
easy.  The  mineral  being  dissolved  in  chlorhydric  acid,  the 
excess  of  acid  was  driven  off  and  the  manganese  was  thrown 
down  by  bromine  in  the  presence  of  an  excess  of  acetate  of 
soda  as  hydrated  sesquioxide;  this  was  redissolved  and 


FROM  MINE  HILL,  NEW  JERSEY.  35 

precipitated  as  ammonio-phosphate  and  weighed  as  pyro- 
phosphate.  The  magnesia  was  separated  from  the  filtrate 
from  the  oxide  of  manganese  (after  it  was  first  ascertained 
that  this  solution  was  entirely  free  from  manganese)  as 
ammonio-phosphate  and  estimated  as  pyrophosphate.  The 
water  was  determined  by  igniting  the  powdered  mineral  in 
a  glass  tube  closed  at  one  end,  about  10  inches  in  length 
with  a  caliber  of  \  of  an  inch.  The  length  of  the  tube 
effected  a  complete  condensation  of  the  water,  which  was 
deposited  on  the  interior  five  or  six  inches  from  the  open  end, 
and  the  tube  and  contents  on  being  weighed  proved  to  have 
suffered  a  loss  of  less  than  one  milligram  by  the  ignition. 
The  water  was  then  dried  out  at  the  ordinary  temperature  in 
vacuo  over  chloride  of  calcium.  To  make  entirely  sure  that 
no  boric  acid  went  off  with  the  water,  I  ignited  a  portion  of 
the  mineral  which  had  previously  been  thoroughly  mixed 
with  about  five  times  its  weight  of  calcined  magnesia  and 
then  covered  with  a  layer  of  pure  magnesia.  The  results 
of  this  experiment  confirmed  the  water  determination  made 
by  the  above  method.  The  boric  acid  was  determined  by 
Stromeyer's  method  as  boro-fluoride  of  potassium.  The  re- 
sults of  the  analyses  are  — 

I.  IT.  III.          IV.          V.          VI.         Mean.    Oxygen. 

Boric  acid 31.89      31.89      22.82 

Manganous  oxide  .    40.08     40.20     40.01      .  .  ,      40.10       9.04 

Magnesia  ....     17.12      16.76     17.21      17.03       6.81 

Water 9.64     9.53       .  .  .        9.59       8.53 

1J8L61 

The  analysis  shows  a  loss  of  1.39  per  cent,  doubtless  due 
chiefly  to  the  imperfections  of  the  method  employed  for 
determining  the  boric  acid.  Calculating  the  loss  as  boric 
acid,  the  total  amount  of  the  acid  is  33.28  per  cent,  and  the 
oxygen  ratio  for  B2O3,  RO,  and  H2O  is  22.82  :  15.85  :  8.53,  or 
3  :  2.08  :  1.12.  The  ratio  3:2:1,  although  not  according 
precisely  with  the  analyses,  is  nevertheless  probably  the  true 
ratio.  It  requires  a  change  of  but  a  few  tenths  of  a  per- 
cent of  water  to  make  this  ratio.  In  fact,  in  what  appeared 
to  be  a  fresher  and  less  altered  specimen  than  that  above 


36  ON  SUSSEXITE,  A   NEW  BORATE. 

analyzed,  I  obtained  but  8.93  per  cent  of  water,  which  would 
change  the  amount  of  boric  acid  calculated  as  loss  to  33.94 
per  cent.  Correcting  the  oxygen  to  correspond  to  these,  we 
have  B2O8 :  RO  :  H2O  =  23.27  :  15.85  :  7.94,  or  almost  ex- 
actly 3  :  2  :  1,  or,  considering  the  water  basic,  a  ratio  of  1  :  1, 
thus  bringing  out  a  most  interesting  relation  between  this 
species  and  native  boric  acid  which  has  the  formula  H3BO3. 
Sussexite  may  be  regarded  as  an  analogous  compound  in  which 
f  of  the  water  is  replaced  by  manganese  and  magnesia,  and 
we  may  write  for  its  formula  [f  (Mn,  Mg)O  +  JH2O]3  .  B2O8, 
or  if  the  water  be  not  considered  basic  it  may  be  represented 
by  2(Mn,  Mg)O  .  B2O3  4-  H2O.*  The  former  I  believe  to  be 
the  correct  view  of  the  composition  of  the  mineral. 

In  some  of  its  physical  and  chemical  characters  sussexite 
resembles  the  mineral  Szaibelyite  from  southern  Hungary. 
This  mineral  is  found  imbedded  in  limestone  in  needle-like 
crystals,  has  a  hardness  of  over  3,  a  density  of  3,  and  is 
a  hydrous  borate  of  magnesia.  One  variety  analyzed  by 
Stromeyer  gave  the  oxygen  ratio  of  B2O8  :  MgO  :  H2O  = 
17  :  14.1  :  4,  or  of  acid  to  bases  including  water  of  17  :  18.1, 
or  nearly  1:1,  requiring  but  a  slight  change  in  the  determi- 
nation of  water  to  make  this  also  a  mineral  analogous  in 
composition  to  boric  acid,  with  which  indeed  it  is  already 
classified  by  Prof.  Dana  in  the  recent  edition  of  his  Min- 
eralogy. Another  member  of  the  group  is  Hydroboracite,  a 
hydrous  borate  of  magnesia  and  lime.  Sussexite  is  at  present 
a  rare  mineral,  but  as  it  occurs  in  a  vein  which  is  extensively 
mined,  there  is  every  reason  to  hope  that  it  may  become  more 
abundant.  Its  pyrognostic  properties  are  so  very  character- 
istic that  it  may  readily  be  distinguished  from  any  other 
mineral  which  it  resembles  in  physical  characters.  In  addition 
to  fibrous  willemite,  I  have  also  found  chrysotile  in  fine  fibers 
imbedded  in  the  calcite  of  Mine  Hill ;  it,  however,  requires 
but  little  familiarity  with  sussexite  to  distinguish  it  at  a 
glance  from  these  species. 

*  The  formula  of  sussexite  is  now  written  RHB03,  R  =  Mn  and  Mg.  A 
little  zinc  was  found  in  a  later  analysis.  —  EDITOR. 


ON  HORTONOLITE, 
A  NEW  MEMBER   OF  THE   CHRYSOLITE   GROUP. 

BY  GEORGE  J.  BRUSH. 

WITH  MEASUREMENTS    AND    OBSERVATIONS   ON 
THE   CRYSTALLINE   FORM   OF  THE   MINERAL. 

BY  JOHN  M.  BLAKE. 
(From  Amer.  Jour.  Sci.,  1869,  vol.  48,  pp.  17-23.) 

SEVERAL  years  since,  Mr.  Silas  R.  Horton  called  my  atten- 
tion to  peculiar  dull  black  crystals  from  an  iron  mine  at  Mon- 
roe, in  Orange  county,  New  York.  On  a  simple  inspection  I 
determined  that  the  crystals  represented  two  species,  the  one, 
magnetite,  in  dodecahedrons;  the  other  a  prismatic  mineral 
with  somewhat  rounded  planes,  which  I  took  to  be  pyroxene. 
At  the  time  I  was  deterred  from  making  a  chemical  examina- 
tion of  the  latter  mineral  by  the  fact  that  the  crystals  appeared 
to  be  very  impure  from  admixture  with  magnetite  and  graph- 
ite. I  have,  however,  never  been  quite  satisfied  that  it  was 
correctly  determined,  and  on  recently  selecting  with  care  a 
portion  of  the  substance  free  from  impurities,  it  proved  to 
gelatinize  with  acids  and  to  have  the  pyrognostic  characters 
of  an  iron  chrysolite ;  and  on  a  more  careful  examination  of 
the  crystals  they  seemed  to  be  orthorhombic  rather  than 
monoclinic,  a  conclusion  confirmed  by  Mr.  Blake's  measure- 
ments further  on. 

The  mineral  has  a  yellow  to  dark  yellowish  green  color  on 
the  fresh  fracture  and  a  vitreous  to  resinous  luster,  although 
the  crystals  have  a  black  coating  and  are  quite  dull.  In  large 
masses  the  mineral  is  sometimes  nearly  black,  but  on  the  thin 
edges  by  transmitted  light  the  color  is  almost  honey-yellow, 
Minute  specks  of  magnetite  are  disseminated  through  the 


38  ON  HORTONOLITE,   A   NEW  MEMBER 

mass  with  occasional  flakes  of  graphite.  The  crystals  are 
sometimes  imbedded  in  calcite,  as  also  associated  in  cavities 
with  dodecahedral  magnetite.  They  are  frequently  half  an 
inch  long  by  one  quarter  broad  and  one  eighth  of  an  inch 
thick,  in  some  instances  much  larger.  H.  =  6.5 ;  sp.  gr.  = 
3.91.  Before  the  blowpipe  in  the  closed  tube  no  change  takes 
place ;  in  the  open  tube  and  on  charcoal  the  mineral  becomes 
dull  and  magnetic,  and  fuses  in  the  platinum  forceps  at  4 ; 
with  borax  and  salt  of  phosphorus,  it  reacts  for  iron  and  silicic 
acid,  and  with  soda  for  manganese.  The  pulverized  mineral 
forms  with  chlorhydric  acid  a  gelatinous  mass  and  is  almost 
completely  decomposed.  Qualitative  analysis  showed  the 
presence  of  silica,  protoxide  of  iron,  manganese  and  magnesia, 
with  a  minute  quantity  of  potash  and  a  trace  of  lime.  It  was 
found  by  pulverizing  the  mineral  and  suspending  the  fine 
powder  in  water  in  a  beaker  and  stirring  with  an  electro- 
magnet of  soft  iron,  that  the  magnetite  could  be  completely 
separated  from  the  silicate.  Two  quantitative  analyses  made 
on  material  thus  prepared  gave  Mr.  Wm.  G.  Mixter  — 

I.  II.  Mean.  Oxygen. 

Silica  33.52        33.66        33.59        17.91 


Magnesia 
Lime 
Potash 
Ignition 


These  analyses  represent  two  different  samplings  by  means 
of  the  electro-magnet,  and  demonstrate  that  the  method  of 
purification  was  as  perfect  as  could  be  desired.  In  the  decom- 
position by  chlorhydric  acid  it  was  found  that  the  separated 
silica  contained  a  very  small  portion  of  undecomposed  mineral, 
and  this  was  consequently  fused  with  carbonate  of  soda  to 
effect  a  complete  decomposition.  The  iron  was  separated  as 
basic  acetate,  redissolved  and  reprecipitated ;  the  manganese  in 


oxide       .    .     44.28 

44.46 

44.37 

9.85^ 

ous  oxide     .      4.72 

3.98 

4.35 

0.98 

a    ....     16.79 

16.56 

16.68 

6.67  I 

17.56 

trace 

'  trace 

0.30 

0.47 

0.39 

0.06  J 

....      0.26 

0.26 

0.26 

99.87 

99.39 

99.64 

OF  THE   CHRYSOLITE   GROUP.  39 

the  solution  was  oxidized  and  separated  by  bromine,  then 
redissolved  and  precipitated  as  phosphate.  The  magnesia  was 
weighed  as  pyrophosphate,  and  the  alkali  determined  by 
Smith's  method.  A  spectroscopic  examination  of  the  concen- 
trated chlorhydric  solution  showed  sodium,  potassium,  and 
calcium  lines  only.  A  direct  determination  of  the  protoxide 
of  iron  on  mineral  selected  as  free  as  possible,  by  aid  of  the 
magnifier,  from  magnetite,  gave  42.69  per  cent ;  this,  consider- 
ing the  difficulty  of  selecting  absolutely  pure  material  and  the 
fact  that  the  mineral,  although  almost  entirely,  is  not  com- 
pletely decomposed  by  acid,  shows  that  the  iron  is  most 
probably  present  only  as  protoxide. 

The  calculation  of  the  oxygen  for  the  mean  of  the  two 
analyses  gives  the  ratio  of  SiO2:  RO  as  17.91 :  17.56  or  1 : 1, 
in  which  the  relation  of  the  iron  to  the  magnesia  is  very  nearly 
as  3  :  2,  and  the  composition  of  the  mineral  is  that  of  an  iron- 
magnesia-manganese  chrysolite.  In  chemical  composition  this 
member  of  the  chrysolite  family  is  between  hyalosiderite  and 
fayalite,  although  it  differs  very  materially  from  both,  as  will 
be  seen  by  comparing  the  analysis  with  these  and  allied 
varieties. 


Only  traces 

of  other 
constituents. 


Si02.  A1203.  FeO.       MnO.  MgO. 

1.  Hyalosiderite      .    .    31.63  2.21  29.71      0.48  32.40 

2.  Dalarne  chrysolite  .    35.20  1.93  35.55     0.58  26.24 

3.  New  chrysolite    .     .     33.59  .  .  .  44.37      4.35  16.68 

4.  Eulysyte  chrysolite     29.16  1.56  55.87      8.47       3.23 

5.  Fayalite,  Fayal  .    .    28.27  3.45           63.80             tr. 

1.  Hyalosiderite,  Walchner,  Schweigger,  Journ.  xxxix,  65.  2.  Analysis 
made  by  Struve,  given  by  Svanberg  in  Ak.  H.  Stockholm,  1848,  p.  2.  3.  This 
article.  4.  A.  Erdmann,  Iviin.,  278.  5.  Rammelsberg,  Min.  Chem.,  435. 

The  new  mineral  contains  more  iron  than  hyalosiderite,  with 
a  correspondingly  smaller  amount  of  magnesia,  while  the  oppo- 
site is  true  with  fayalite.  It  more  nearly  approaches  the 
variety  of  iron-manganese  chrysolite  described  by  Erdmann  as 
occurring  near  Tunaberg  in  Sweden,  associated  with  garnet 
and  augite  forming  a  rock  which  has  been  named  eulysyte; 
from  this,  however,  it  differs  in  containing  13  per  cent  more 


40  ON  HORTONOLITE,   A   NEW  MEMBER 

magnesia,  and  about  16  per  cent  less  iron  and  manganese,  and 
no  lime.  The  mineral  therefore,  forms  a  marked  variety  of 
iron-magnesia-manganese  chrysolite. 

In  view  of  these  facts,  it  is  proper  to  designate  this  new 
variety  with  a  special  name,  and  I  propose  for  it  the  name 
ffortonolite,  after  Mr.  Horton,  who  first  discovered  the  min- 
eral. If  found  in  quantity,  this  may  prove  to  be  a  valuable 
iron  ore,  if  smelted  with  more  basic  or  calcareous  ores.  It  is 
free  from  undesirable  impurities,  while  it  contains  a  con- 
siderable amount  of  manganese.  There  is  reason  to  believe 
that  it  may  occur  in  sufficient  abundance  to  be  of  economic 
importance. 

It  gives  me  pleasure  to  acknowledge  my  indebtedness  to 
Mr.  Horton  for  kindly  supplying  me  with  specimens  of  this 
mineral  for  examination ;  to  Mr.  W.  G.  Mixter,  assistant  in 
the  Sheffield  Laboratory,  for  aid  in  the  chemical  investigation ; 
and  to  Mr.  John  M.  Blake  for  his  discussion  of  the  crystallo- 
graphic  characters  of  the  mineral  which  here  follows. 

Observations  on  the  crystalline  form,  optical  characters,  and 
cleavage  of  Hortonolite ;  By  JOHN  M.  BLAKE. 

The  examination  and  measurement  of  crystals  of  Hortono- 
lite, which  were  placed  in  my  hands  for  this  object  by  Prof. 
Brush,  show  unmistakably  that  the  mineral  belongs  to  the 
chrysolite  group.  A  comparison  was  made  with  other  mem- 
bers of  the  group,  to  determine  its  relation  to  them.  For  this 
purpose,  several  species  were  measured,  crystals  having  been 
placed  at  my  disposal  by  Prof.  Brush.  The  points  compared 
were  the  occurrence  and  proportional  development  of  planes, 
and  to  some  extent  the  optical  properties  and  cleavages.  This 
examination  is  not  yet  completed,  but  it  being  desired  that  a 
description  of  this  mineral  should  be  furnished  as  soon  as 
possible,  the  results  must  be  given  in  a  form 'that  will  require 
the  least  explanation. 

The  observed  planes  on  this  variety  are : 

J,    010  m,    110  k,   021  g,   212 

o,  001  d,    101  e,    111 


OF  THE   CHRYSOLITE   GROUP. 


41 


A  deposition  of  some  foreign  substance  had  destroyed  the 
brilliancy  of  the  planes,  and  this  could  not  be  entirely  removed 
so  that  they  would  give  perfect  reflections ;  and,  besides  this, 
some  parts  of  crystals  appear  to  have  been  originally  rounded. 


FIGURE  1. 


FIGURE  2. 


FIGURE  3. 


Figure  1  is  proportioned  from  some  of  the  larger  crystals. 
They  were  partially  imbedded,  so  that  but  a  portion  of  the 
planes  could  be  distinguished  on  any  one  of  them.  The  inter- 
sections with  the  other  planes  satisfactorily  determined  the 
planes  e  on  these  particular  crystals. 

Figure  2  is  a  common  form  of  the  medium-sized  crystals. 
The  upper  planes  on  the  front  side,  can  be  explained  as  the 
planes  #,  the  directions  of  their  intersections  with  m  and 
an  approximate  measurement  of  their  inclination  on  b  leaving 
little  doubt  of  their  identity  with  this  plane. 

Figure  3  represents  an  occasional  form.  It  is  introduced 
to  show  the  variation  in  crystals  upon  the  same  specimen. 
Another  small  crystal  had  the  prismatic  planes  nearly  equal 
in  breadth,  and  k  largely  developed,  while  the  other  terminal 
planes  were  rounded. 

Notwithstanding  this  great  variation  in  development,  the 
crystals  do  not  at  all  resemble  those  of  hyalosiderite  in  habit ; 
neither  do  they  resemble  certain  crystals  occurring  as  furnace 
products,  which  I  have  directly  compared  with  them. 

NOTE.  —  Mr.  Blake's  article  has  been  shortened  by  omitting 
the  table  of  measured  and  calculated  angles  and  the  discussion 
of  the  optical  properties  of  the  mineral.  —  EDITOR. 


ON   GAHNITE   FROM   MINE   HILL,   FRANKLIN 
FURNACE,   NEW   JERSEY. 

BY  GEORGE  J.  BRUSH. 
(From  Am.  Jour.  Sci.,  1871,  vol.  1,  pp.  28-29.) 

THE  rare  species  Gahnite  has  been  again  found  at  a  new 
locality  in  a  cross-cut  made  by  the  New  Jersey  Zinc  Co.  from 
the  valley  of  the  Wallkill  river  to  an  opening  on  the  south 
end  of  Mine  Hill.  I  collected  specimens  at  this  locality  in 
the  summer  of  1869,  and  by  blowpipe  examination  at  that 
time  determined  the  mineral  to  be  a  zinc  spinel. 

The  mineral  differs  in  its  crystalline  characters  from  the 
specimens  of  other  localities  in  the  frequent  occurrence  of 
the  cubic  plane ;  in  fact  the  cubic  planes  are  often  the  largest, 
so  that  the  crystals  are  cubes  with  truncated  dodecahedral 
edges  and  only  small  octahedral  planes.  There  are  also  minute 
planes  of  the  trapezohedron  (211),  truncating  the  edges  of  the 
dodecahedron;  also  others  of  the  trigonal-trisoctahedron  (331). 
Besides  these  there  are  sometimes  two  planes  between  the 
cubic  and  the  octahedral,  which  appear,  from  examination 
and  approximate  measurements  by  Prof.  Dana,  to  belong  to 
the  forms  (411)  and  (811).  Their  surfaces  are  rounded, 
and  feeble  in  luster,  and  generally  they  are  blended  in  a 
single  curved  plane,  consequently  the  measurements  are  not 
entirely  satisfactory.  The  inclinations  on  a  cubic  plane, 
obtained  by  Prof.  Dana,  are  for  (411)  160°  30',  for  (811), 
170°  30'. 

The  crystals  vary  in  diameter  from  an  eighth  of  an  inch  to 
over  an  inch  and  a  half;  generally,  however,  they  are  less 
than  half  an  inch.  The  color  of  the  crystals  is  blackish-green ; 
in  thin  fragments,  olive-green.  Hardness  =  7.5 ;  specific 
gravity  =  4.89-4.91. 


ON  GAHNITE  FROM  FRANKLIN  FURNACE,  N.  J.       43 

Before  the  blowpipe  the  mineral  is  infusible.  With  the 
fluxes  it  reacts  for  iron  and  manganese;  and  with  soda 
on  charcoal  it  gives  a  zinc  coating. 

The  analysis  in  the  wet  way  was  made  by  Mr.  Joseph  S. 
Adam  of  this  laboratory.  The  mineral  was  decomposed  by 
fusion  with  bisulphate  of  potash.  The  silica  was  separated 
in  the  usual  manner,  and  the  iron  and  alumina  thrown  down 
as  basic  acetates,  and  this  precipitate  was  examined  to  insure 
purity.  The  iron  was  determined  by  titration  with  perman- 
ganate of  potash.  From  the  acetic  solution  the  manganese 
was  separated  by  bromine,  and  the  zinc  was  thrown  down 
from  the  filtrate  by  sulphide  of  ammonium.  The  small  amount 
of  magnesia  was  determined  as  pyrophosphate,  care  having 
been  first  taken  to  separate  the  minute  traces  of  it  which  were 
found  precipitated  with  the  alumina. 

Two  analyses  by  J.  S.  Adam  gave : 

I.  II.  Mean.         Oxygen.      Ratio. 

Alumina 49.86     

Ferric  oxide     .....       8.83       °  °°      °  K0       °  Krr  < 

Zinc  oxide 39.39 

Manganous  oxide      .     .     .       1.20      1.07      1.13      0.25  }     8.12 

Magnesia 0.12 

Silica 0.71 

100.11     99.50    99.81 

This  gives  the  relation  of  the  oxygen  of  RO  and  R2O3  as 
8.12  :  25.77,  or  1  :  3.17,  which  would  indicate  that  a  small 
portion  of  the  iron  was  present  as  protoxide.  We  have  but  to 
assume  1.56  per  cent  of  the  Fe2O3  in  the  analysis  to  have 
existed  as  FeO  in  the  mineral  to  reduce  the  ratio  to  exactly 
1:  3. 

This  variety  of  gahnite  shows  a  larger  percentage  of  zinc 
than  any  heretofore  analyzed,  and  is  unique  in  its  cubic  habit. 
It  is  associated  with  black  mica,  apatite,  calcite,  and  a  brownish 
variety  of  chrysolite.  A  partial  analysis  of  this  chrysolite  by 
W.  G.  Mixter  shows  it  to  be  a  unisilicate  of  iron,  manganese, 
magnesia,  and  zinc,  probably  related  to,  and  possibly  identical 


44       ON  GAHNITE  FROM  FRANKLIN  FURNACE,   N.   J. 

with  the  zinciferous  chrysolite  described  by  Prof.  W.  T.  Roap- 
per.*  A  tin- white  metallic  mineral  imbedded  in  some  of  the 
gahnite  crystals  proved  to  have  the  pyrognostic  characters 
of  leucopyrite. 


FIGURE  1. 


FIGURE  2. 


NOTE.  —  As  only  a  few  of  the  gahnite  crystals  described 
by  Professor  Brush  were  found  and  as  they  are  so  unusual  in 
their  development,  the  liberty  has  been  taken  of  introducing  two 
figures  of  the  crystals,  drawn  by  Mr.  P.  B.  Condit  of  the  Sheffield 
Laboratory.  Figure  2  represents  the  largest  crystal  of  the  suite, 
which  has  a  diameter  of  a  little  over  1  inches.  —  EDITOR. 


*  Amer.  Jour.  Sci.  (2),  vol.  50,  p.  35. 


ON  THE   CHEMICAL    COMPOSITION  OF 
DURANGITE. 

BY  GEORGE  J.  BRUSH. 
(From  Amer.  Jour.  Sci.,  1876,  vol.  11,  pp.  464-465.) 

IN  an  article  *  on  this  rare  mineral,  published  in  1869,  I 
expressed  the  hope  to  make  further  examination  of  its  chemi- 
cal composition  whenever  sufficient  material  could  be  obtained 
for  this  purpose.  Several  years  elapsed  before  any  new  dis- 
coveries of  the  mineral  in  Durango  were  made.  I  am  again 
indebted  to  Mr.  Henry  G.  Hanks  of  San  Francisco  for  a  new 
supply  of  the  crystals  obtained  in  recent  explorations.  These 
crystals  are  much  smaller  than  those  previously  examined, 
being  from  one  to  three  millimeters  in  diameter,  and  they  are 
of  a  darker  shade  of  color.  The  former  were  loose  detached 
crystals,  while  these  are  associated  with,  and  in  some  cases 
attached  to,  rolled  fragments  of  crystallized  hematite  and 
cassiterite.  The  density  of  the  small  dark  colored  crystals  is 
4.07,  while  that  of  the  purest  of  the  bright  colored  crystals 
before  described  is  3.937.  In  all  other  physical  characters 
there  is  a  perfect  correspondence  between  the  two  varieties. 

The  chemical  examination  of  the  dark  colored  small  crystals 
has  been  undertaken,  at  my  request,  by  my  assistant,  Mr. 
George  W.  Hawes,  first  to  estimate  the  amount  of  fluorine  in 
the  mineral,  which  in  two  determinations  he  found  to  be  7.67 
and  7.49  per  cent,  and  Mr.  Hawes  has  also  placed  at  my  dis- 
posal for  this  article  a  complete  analysis  of  this  variety  of  the 
mineral.  The  fluorine  was  determined  directly  by  Wohler's 
method  as  modified  by  Fresenius.  To  determine  the  arsenic 

*  Amer.  Jour.  Sci.  (2),  vol.  48,  p.  179. 


46 


ON  THE   CHEMICAL   COMPOSITION 


acid,  and  the  bases,  the  mineral  was  decomposed  by  sulphuric 
acid,  and  the  arsenic  weighed  as  sulphide ;  the  alumina,  iron, 
and  manganese  obtained  in  the  analysis  were  carefully  ex- 
amined to  ascertain  their  purity.  The  soda  and  lithia  were 
weighted  as  sulphates  and  then  converted  into  chlorides  and 
separated  by  ether  and  alcohol. 

The  results  of  the  analysis  are  as  follows : 


Arsenic  acid 53.11 

Alumina 17.19 

Ferric  oxide 9.23 

Manganic  oxide 2.08 

Soda 13.06 

Lithia 0.65 

Fluorine 7.67 

102.99 


n. 


7.49 


The  percentage  of  fluorine,  7.67,  corresponds  to  3.23  per  cent 
of  oxygen,  which  being  subtracted,  the  analysis  foots  up  to 
99.76.  Calculating  the  percentages  of  the  elements  we  have 
the  following : 


Atomic  ratio 


As. 

34.63 
0.462 

0.462 


Al. 

9.18 
0.335 


Fe. 

6.50 
0.116 


Mn. 

1.45 

0.026 


Na. 

9.69 
0.421 


Li. 

0.31 
0.044 


0.477 


0.465 


Fl. 

7.67 
0.404 

0.404 


The  ratio  of  As  :  Al  +  Fe  +  Mn  :  Na  +  Li :  F  is  very 
nearly  1 :  1 :  1 :  1 ;  hence  the  formula  may  be  written  Na 
[AlF]AsO4,  in  which  a  little  of  the  Na  and  Al  are  re- 
placed, respectively,  by  isomorphous  Li  and  Fe  and  Mn. 

This  is  a  confirmation  of  the  conclusion  drawn  by  me  from 
the  analysis  of  the  lighter  colored  crystals  described  in  the 
original  paper.* 

The  mean  of  my  two  analyses  gave : 


Loc.  cit. 


OF  DURANGITE.  47 

Arsenic  acid 54.16 

Alumina 20.35 

Ferric  oxide 4.92 

Manganic  oxide 1.43 

Soda 11.76 

Lithia 0.75 

Fluorine undetermined. 

The  variety  examined  by  Mr.  Hawes  contains  less  alumina, 
and  considerably  more  iron,  which  accounts  for  its  darker 
color  and  slightly  higher  specific  gravity.  His  results  prove 
the  mineral  to  be  an  arseniate  analogous  in  chemical  compo- 
sition to  amblygonite,  as  suggested  in  my  previous  paper. 

NOTE.  —  Durangite  contains  a  little  hydroxyl,  as  was  proved  by 
heating  the  mineral  in  a  closed  tube  with  freshly  ignited  lime 
and  obtaining  a  deposit  of  water.  The  amount  of  water  given  off 
is  small,  and  indeed  only  0.51  per  cent  of  H20  is  needed  in  the 
analysis  given  above  to  yield  a  ratio  of  As  :  F  +  OH  =  1:1.  At 
the  time  the  article  on  durangite  was  written  fluorine  was 
supposed  to  replace  oxygen,  and  the  isomorphous  relation  of 
fluorine  and  hydroxyl  was  not  known.  —  EDITOR. 


ON  A  NEW  AND  REMARKABLE  MINERAL  LO- 
CALITY AT  BRANCHVILLE,  IN  FAIRFIELD 
COUNTY,  CONNECTICUT;  WITH  A  DESCRIP- 
TION OF  SEVERAL  NEW  SPECIES  OCCUR- 
RING THERE.  — FIRST  PAPER.* 

BY  GEORGE  J.  BRUSH  AND  EDWARD  S.  DANA. 
(From  Am.  Jour.  Sci.,  1878,  vol.  16,  pp.  33-46.) 

Historical  Note. 

THE  new  locality  of  manganesian  phosphates,  which  we  shall 
describe  in  this  and  following  papers,  is  situated  near  the 
village  of  Branchville,  in  the  town  of  Redding,  Fairfield 
County,  Connecticut.  Its  remarkable  character  will  be  evi- 
dent from  the  statement  that  we  have  thus  far  discovered, 
among  the  material  which  we  have  obtained  from  there,  no 
less  than  six  new  and  well  defined  species,  besides  many 
other  known  species  of  more  or  less  rarity. 

The  locality  was  first  opened  some  two  years  since  by  Mr. 
A.  N.  Fillow,  upon  whose  land  it  is  situated,  and  who  made 
considerable  excavations  in  the  search  for  mica  of  commercial 
value.  Only  a  limited  quantity  of  this  was  obtained,  so  that 
the  work  was  finally  discontinued  and  the  opening  filled  up ; 
by  which  means  the  ledge  was  buried  under  six  to  eight  feet 
of  soil.  With  most  commendable  thoughtfulness,  however, 
he  laid  aside  and  preserved  a  large  number  of  specimens 
which  seemed  to  him  to  be  of  some  interest.  In  the  latter 

*  The  Branchville  Papers  are  five  in  number,  four  of  which  appeared 
between  the  years  1878  and  1880,  while  the  fifth  one  did  not  appear  until 
1890.  They  are  here  brought  together,  but  in  order  to  shorten  them  some- 
what it  has  been  necessary  to  omit  descriptions  of  methods  of  analysis,  tables 
of  measured  and  calculated  angles  and  some  of  the  less  important  matter. 
—  EDITOR. 


FIRST  BRANCHVILLE  PAPER.  49 

part  of  the  summer  of  1877,  Prof.  J.  D.  Dana  visited  the 
region  and  his  attention  was  called  by  Mr.  Fillow  to  the 
collection  of  minerals  mentioned,  and  by  him  several  speci- 
mens were  brought  to  New  Haven.  Later,  Rev.  John 
Dickinson,  of  Redding,  the  adjoining  village,  happened  to 
visit  the  locality  and  obtained  a  considerable  amount  of  the 
minerals,  some  of  which  he  sent  to  New  Haven  for  deter- 
mination. It  was  not,  however,  until  the  early  spring  of 
the  present  year  that  we  were  able  personally  to  visit  the 
locality.  Appreciating  then  the  unusual  interest  connected 
with  it,  we  immediately  made  arrangements  with  Mr.  Fillow 
to  uncover  the  ledge  and  to  go  forward  with  the  exploration 
as  thoroughly  as  possible.  We  have  now  pushed  the  matter 
as  far  as  is  practicable  for  the  present,  but  later  in  the  season 
we  hope  to  accomplish  more.  The  result  of  our  work  has 
been  to  place  in  our  hands  a  large  amount  of  material,  in 
the  examination  of  which  we  are  at  present  engaged,  and  we 
are  now  ready  to  make  public  a  portion  of  the  results.  In 
addition  to  the  material  we  have  personally  obtained,  we 
have,  through  the  liberality  of  Mr.  Dickinson,  come  into  the 
possession  of  a  large  number  of  additional  specimens  collected 
by  himself  before  our  first  visits  to  B ranch ville.  These  have 
been  of  the  greatest  service  to  us  in  the  study  of  the  species 
occurring  at  the  locality,  and  we  would  here  express  our  great 
appreciation  of  his  generosity.  We  would  also  mention  our 
obligations  to  Mr.  Fillow  and  his  brother,  who  have  been 
most  careful  in  obtaining  the  best  results  possible  in  the 
explorations  of  which  they  have  taken  charge. 

Brief  general  description. 

All  the  minerals  which  we  have  obtained  are  from  a  single 
vein  of  albitic  granite,  and  the  line  along  which  the  explora- 
tions have  been  carried  does  not  exceed  twenty  feet.  The 
general  description  of  the  vein  and  of  the  minerals  which 
compose  it — with  the  exception  of  the  manganesian  phos- 
phates and  the  immediately  associated  species — we  reserve 

4 


50  FIRST  BRANCHVILLE  PAPER. 

for  a  later  paper;  we  will  mention,  however,  that  outside  of 
these  we  have  identified  the  following  species : 

Albite,  quartz,  microcline  in  large  masses,  a  hydro-mica 
near  damourite  having  a  peculiar  concentric  spherical  struc- 
ture, spodumene  in  crystals  weighing  one  to  two  hundred 
pounds,  cymatolite  as  a  result  of  the  decomposition  of 
spodumene  crystals,  sometimes  nine  inches  in  width,  apatite, 
microlite  (sp.  gr.  =  6),  columbite  (sp.  gr.  =  5.6)  apatite, 
garnet,  tourmaline  and  staurolite. 

The  manganesian  phosphates  and  related  minerals  occur  in 
nests  imbedded  in  the  albite.  A  single  deposit  yielded  almost 
all  the  material  obtained,  it  being  probable  that  what  came 
out  as  the  result  of  our  work  was  a  part  of  the  same  body  of 
minerals  which  Mr.  Fillow  had  blasted  into  two  years  before. 
A  second  deposit  will  be  mentioned  later  as  having  furnished 
the  lithiophilite. 

The  minerals  which  form  the  mass  of  the  first  mentioned 
bed  are :  —  Eosphorite,  dickinsonite,  triploidite  and  rhodochro- 
site.  Of  these,  the  first  three  are  new  and  are  described  at 
length  in  this  paper.  These  four  minerals,  together  with 
quartz,  occur  associated  in  the  most  intimate  manner  possible, 
it  being  not  at  all  unusual  to  find  all  of  them  in  a  single  hand 
specimen.  This  is  especially  true  of  the  three  new  minerals : 
the  eosphorite  is  often  found  in  crystals  entirely  imbedded 
in  the  dickinsonite,  and  again  the  finely  disseminated  plates 
of  dickinsonite  give  a  green  color  to  much  of  the  massive 
eosphorite.  Quartz  is  also  contained  in  much  of  the  massive 
eosphorite,  thus  giving  it  a  very  anomalous  appearance ;  it 
also  forms  the  mass  in  which  the  triploidite  crystals  are  im- 
bedded—  both  these  points  are  spoken  of  more  particularly 
later.  Quartz  is  also  often  associated  with  the  rhodochrosite, 
that  mineral  being  disseminated  in  crystalline  grains  through 
the  quartz  in  which  occasional  brilliant  cubes  of  pyrite  are 
also  imbedded. 

In  addition  to  the  above  minerals,  as  original  constituents 
of  the  same  deposit,  are  amblygomte  (hebronite),  and  a  phos- 
phate of  manganese  ismorphous  with  scorodite  which  we  shall 


FIRST  BRANCHVILLE  PAPER.  51 

describe  under  the  name  reddingite.  As  secondary  products 
we  have  apatite  and  quartz  coating  together  crystals  of 
eosphorite,  vivianite  in  thin  layers  and  crystals,  besides  other 
species,  which  as  yet,  owing  to  lack  of  sufficient  material  for 
examination,  we  have  been  unable  to  determine. 

Furthermore,  there  are  a  variety  of  alteration  products: 
each  one  of  the  manganesian  phosphates  yields  on  alteration  a 
black  or  purple  phosphate  of  manganese  and  iron  sequioxides, 
and  the  rhodochrosite  gives  a  pseudomorph  of  hydrated  oxides. 

The  second  smaller  nest  discovered  consisted  almost  exclu- 
sively of  lithiophilite.  Of  the  previously  mentioned  minerals 
rhodochrosite  is  the  only  one  we  have  observed  with  it,  and 
that  occurs  very  sparingly.  In  addition,  however,  a  peculiar 
green  manganiferous  apatite,  spodumene,  and  cymatolite  are 
intimately  associated  with  the  lithiophilite,  besides  the  black 
phosphate  produced  from  its  oxidation,  and  occasional  crystals 
of  uraninite  and  both  green  and  yellow  hydrated  phosphates 
of  uranium. 

From  the  large  amount  of  black  oxidized  material,  rich  in 
lithia,  found  with  the  first  deposit  it  is  probable  that  lithio- 
philite, or  some  other  similar  mineral  of  the  triphylite  group, 
formed  one  of  the  original  constituents  of  that  mass.  In  fact 
it  was  the  discovery  of  lithia  in  the  black  product  of  decom- 
position, and  its  absence  in  eosphorite,  triploidite  and  dickin- 
sonite,  which  led  us  to  make  further  search  for  the  source  of 
this  alkali.  Fortunately,  in  the  deepest  part  of  our  explora- 
tions in  the  vein  we  struck  a  small  nest  which  afforded  us  the 
fresh  unaltered  mineral. 

We  wish  here  to  express  our  great  obligations  to  Messrs. 
Samuel  L.  Penfield  and  Horace  L.  Wells  of  the  Sheffield 
Laboratory,  for  the  excellent  analyses  which  their  enthusias- 
tic devotion  to  the  work  has  enabled  us  to  present  in  this 
paper.  The  carrying  through  of  these  analyses  has  involved 
in  many  cases  more  than  usual  difficulty,  and  we  appreciate 
fully  to  what  an  extent  the  value  of  this  article  is  dependent 
upon  the  skill  and  patient  care  with  which  these  difficulties 
have  been  overcome. 


52  FIRST  BRANCHVILLE  PAPER. 

1.      EOSPHORITE. 

General  physical  characters.  —  Eosphorite  occurs  in  pris- 
matic crystals,  sometimes  of  considerable  size,  which  belong 
to  the  orthorhombic  system.  They  show  a  nearly  perfect 
macrodiagonal  cleavage.  It  also  and  more  commonly  occurs 
massive,  some  specimens  showing  the  cleavage  finely,  but 
graduating  into  others  which  are  closely  compact.  The  hard- 
ness is  5.  For  the  specific  gravity,  three  perfectly  pure  rose- 
colored  specimens  gave  3.124,  3.134,  and  3.145 ;  mean,  3.134. 
The  luster  of  crystallized  specimens  is  vitreous  to  sub- 
resinous,  upon  cleavage  surfaces  exceedingly  brilliant ;  of  the 
massive  mineral  often  greasy.  The  color  of  the  crystals  is 
pink,  some  having  the  bright  shade  common  in  rose-quartz, 
while  others  are  paler  and  have  a  yellow  to  gray  hue;  the 
smallest  crystals  are  nearly  colorless.  The  massive  compact 
mineral  is  pale  pink,  also  grayish,  bluish,  and  yellowish-white, 
and  white.  Some  varieties  closely  resemble  in  color  and  luster 
green  elseolite ;  the  green  color,  however,  is  shown  by  the 
examination  of  thin  sections  under  the  microscope  to  be  due 
to  finely  disseminated  scales  of  dickinsonite.  Some  varieties 
again  are  rendered  impure  by  the  presence  of  quartz  through 
the  mass,  and  they  then  have  a  whitish  color  and  granular 
texture  ;  this  subject  is  expanded  in  a  later  paragraph. 

The  mineral  is  transparent  to  translucent.  The  streak  is 
nearly  white,  and  the  fracture  uneven  to  subconchoidal. 

Description  of  crystals.  —  Specimens  of  crystallized  eosphor- 
ite  are  rare.  The  most  of  those  obtained  seem  to  have  come 
from  a  single  cavity,  the  crystals  standing  free,  and  projecting 
to  some  length.  Again  they  are  found  completely  imbedded, 
as,  for  instance,  in  dickinsonite.  These  crystals  are  in  gen- 
eral small ;  but  occasionally  imperfect  crystals  of  a  consider- 
able size  are  met  with,  one  of  these  exposes  a  width  of  about 
an  inch,  and  is  two  inches  long;  in  another,  a  single  plane 
has  a  width  of  nearly  two  inches.  The  planes  are  seldom 
well  polished,  and  only  in  rare  cases  are  exact  measurements 
obtainable.  This  is  due  in  part  to  the  fact  that  the  surfaces 


FIRST  BRANCHVILLE  PAPER. 


53 


of  the  crystals  are  often  coated  with  drusy  quartz,  and 
again  with  minute  crystals  of  apatite,  and  also  because  the 
prismatic  planes  almost  always,  and  the  pyramidal  planes 
very  commonly,  are  finely  striated.  This  striation  of  the 
prismatic  planes  is  a  marked  characteristic  and  gives  rise  to 
rounded  barrel-shaped  crystals  analogous  to  those  observed 
of  tourmaline  and  many  other  species. 

The  crystals  are  invariably  prismatic  in  habit,  and  show  but 
one  terminated  extremity ;  in  this  respect  they  differ  from  the 
ordinary  children! te  of  Tavistock,  to  which  it  will  be  shown 
they  are  closely  related.  The  general  form  is  shown  in  fig- 
ure 1. 


rH^ 

^ 
a 

_j/75rA 

m 

g 

b 

] 

?ior 

RE    1. 

Eosphorite. 
Branchville. 

FIGURE  2. 

Childrenite. 
Hebron,  Me. 


FIGURE  3. 

Childrenite. 
Tavistock. 


The  crystallographic  measurements  and  also  the  optical 
examination  '  prove  that  the  crystals  belong  to  the  ORTHO- 
RHOMBIC  SYSTEM. 

The  fundamental  angles  were  obtained  from  measurements 
on  a  small  crystal  whose  pyramidal  planes  gave  excellent 
reflections.  The  mean  of  a  considerable  number  of  readings, 
whose  extremes  differed  by  only  1J',  was  taken  in  each  case. 
A  goniometer  provided  with  two  telescopes  was  always 
employed. 

These  angles  are  as  follows : 

p  A  j>'"  or  111  A  1T1  =  46°  27'  45" 
^'    or  111  A  Til  =61°    1' 64" 


54  FIRST  BRANCHVILLE  PAPER. 

From  these  the  following  axial  ratio  is  obtained :  — 

a  :  b  :  c  =  0.77680  :  1  :  0.51501 
The  observed  planes  are  as  follows : 

a,  100  m,   110  p,   111  s,   121 

fc,   010  g,     120  q,  232 

Eosphorite  is  in  crystalline  form  closely  homoeomorphous 
with  childrenite.  Figure  2  represents  the  common  form  of 
the  childrenite  from  Hebron,  Maine,  as  we  have  found  from 
an  examination  of  the  specimens  in  New  Haven.  The  crys- 
tals are  sometimes  terminated  at  both  extremities  as  here 
represented.  It  is  placed  in  such  a  position  as  to  correspond 
with  the  eosphorite,  the  pyramid  s  being  identical  in  the 
two,  as  are  also  the  prisms.  Figure  3  shows  a  common  form 
of  the  Tavistock  crystals;  other  crystals  have  the  plane  b 
present  and  resemble  figure  2  more  closely  in  habit.  The 
angles  given  below  show  the  close  relation  in  form  between 
childrenite  and  eosphorite. 

,,      .      ..  Childrenite.  Childrenite.  Childrenite. 

Tavistock  (Cooke).    Hebron  (Cooke).    Tavistock  (Miller). 

m*m  75°  41'  75°  24'  74°  20'  75°  46' 

s  A  s'"  81°  18'  81°  20'  80°  38'  82°    8' 

s  A   s'  49°  34'  49°  50'  50°  36'  49°  56' 

s  A  s"  101°  33'  101°  43'  101°  36'  102°  41' 

In  order  to  bring  the  crystals  of  childrenite  into  this  posi- 
tion the  dome  n  of  Miller  is  made  the  unit  prism.' 

Optical  properties.  —  A  careful  examination  in  the  stauro- 
scope  proved  that  the  three  axes  of  elasticity  coincide  with 
the  crystalline  axes,  showing  that  the  crystals  are  really  ortho- 
rhombic.  The  optic  axes  lie  in  the  macrodiagonal  section,  or 
plane  of  cleavage,  the  acute  bisectrix  being  normal  to  the 
brachypinacoid,  and  the  obtuse  bisectrix  consequently  to  the 
basal  plane.  The  axial  angle  could  not  be  obtained  with  very 
great  accuracy,  owing  to  the  fact  that  the  best  sections  left 
much  to  be  desired  in  the  way  of  clearness.  The  measure- 
ments gave : 


FIRST  BRANCHVILLE  PAPER. 


55 


2E  =  54°  30' 

"  =  60°  30' 


red  rays, 
blue  rays. 


The  dispersion  of  the  axes  is  strong,  v  >  p ;  the  character  of 
the  double-refraction  is  negative. 

An  examination  of  a  parallelepiped  cut  with  its  edges  par- 
allel to  the  three  axes  of  elasticity  (crystalline  axes)  showed  a 
very  distinct  trichroism.  The  axial  colors  are  as  follows : 

For  vibrations  parallel  to  a   (that  is  b)  yellowish. 

b    (that  is  a)  deep  pink. 
t   (that   is    c)    faint    pink    to    nearly 
colorless. 

Chemical  composition.  —  The  finest  of  the  pink  crystals  were 
used  for  the  chemical  examination  of  eosphorite,  which  was 
made  by  Mr.  Samuel  L.  Penfield,  assistant  in  the  Sheffield 
Laboratory. 

Two  analyses  gave : 


I. 

II. 

Mean. 

Keianve  numoer  01  acorns  caic 
lated  from  the  mean. 

P2O6 

31.10 

30.99 

31.05 

0.219 

1.00 

1 

A1203 

21.99 

22.40 

22.19 

0.216 

0.99 

1 

FeO 

7.42 

7.39 

7.40 

0.103  - 

MnO 
CaO 

23.47 
0.54 

23.56 
0.54 

23.51 
0.54 

0.331  , 
0.010 

0.449 

2.05 

2 

Na20 

0.33 

0.33 

0.33 

0.005  - 

H20 

15.66 

15.54 

15.60 

0.866 

3.95 

^ 

100.51   100.75   100.62 

The  ratio  P2O5  :  A12O3  :  RO  :  H2O  =  1:1:2:  4  corre- 
sponds to  the  empirical  formula  R2Al2P2Oi0  .  4H2O,  which  may 
be  written  A12P2O8  4-  2H2RO2  +  2  aq.  The  analogy  in  the 
composition  of  eosphorite  to  that  of  childrenite  suggests,  how- 
ever, that  the  better  way  of  writing  the  formula  is  : 

H2E02 


fBAOs          (H2K02 
{A12P208        tH6Ala06 


In  the  formula  R  corresponds  to  Mn  and  Fe  with  small  quan- 
tities of  Ca  and  Na2 ;  the  ratio  for  Mn  :  Fe  +  Ca  +  Na2  =  3  : 
1,  and  for  Mn  :  Fe  =  10  :  3 :  for  the  last  ratio  the  above  form- 
ula requires : 


56 


FIRST  BRANCHVILLE  PAPER. 


Eosphorite. 
Calculated  from 
the  formula. 

30.93 

Childrenite, 
analyzed  by 
Rammelsberg. 

28.92 

Childrenite, 
analyzed  by 
Church. 

30.65 

22.35 

14.44 

15.85 

7.24 

30.68 

(Fe203  3.51 
(FeO   23.45 

23.80 

9.07 

7.74 

.  .  . 

0.14 

1.03 

15.68 

16.98 

17.10 

100.00 

100.23 

99.33 

G.  =  3.134 

G.  =3.247 

G.  =  3.22 

A1208 
FeO 

MnO 
MgO 
H20 


The  identity  between  the  crystalline  form  of  eosphorite  and 
that  of  childrenite  has  been  pointed  out  in  a  preceding  para- 
graph, and  the  analogy  between  them  in  chemical  composition, 
and  at  the  same  time  the  wide  difference,  will  be  seen  from  the 
above.  The  ratios  obtained  from  the  analyses  of  Rammelsberg 
and  Church  for  the  childrenite  from  Tavistock  and  that  of 
eosphorite  are  as  follows : 


Childrenite  j 
Eosphorite 


PA- 

3 
4 
1 


E203. 

2 
3 
1 


Childrenite  \  ?£' 
(_  On. 

Eosphorite 


RO. 

:  8 
:  9 
:  2 

R203  +  RO. 

3i  : 
3  : 
3  : 


H,O. 
15 

18 
4    and 


H20. 

5 

4* 
4 


It  can  hardly  be  doubted  from  the  above  relations  and  the 
other  facts  given  that  the  two  species  are  in  fact  isomorphous, 
although  the  uncertainty  that  hangs  over  the  composition  of 
childrenite  makes  it  useless  to  compare  the  formulas.  It  is 
quite  possible  that,  when  the  composition  of  childrenite  shall 
be  definitely  settled,  it  will  be  found  to  be  analogous  to  that 
given  for  eosphorite.*  It  cannot  be  questioned,  however,  that 
the  two  species,  though  closely  isomorphous,  are  at  the  same 
tune  perfectly  distinct:  the  physical  characters,  the  habit  of 


*  This  prediction  has  been  found  to  be  true.    See  page  124. — EDITOR. 


FIRST  BRANCHVILLE  PAPER.  57 

the  crystals,  and  method  of  occurrence  speak  emphatically 
for  this.  Chemically,  too,  they  are  not  to  be  confounded, 
although  they  may  be  similar  compounds;  eosphorite  is 
essentially  a  phosphate  of  aluminum  and  manganese,  and 
childrenite  of  aluminum  and  iron. 

Pyrognostics. — In  the  closed  tube  eosphorite  decrepitates, 
whitens,  gives  off  abundance  of  neutral  water,  and  the  residue 
turns  first  black,  then  gray,  and  finally  liver-brown  with  a 
metallic  luster,  and  becomes  magnetic.  B.B.  in  the  forceps  it 
cracks  open,  sprouts  and  whitens,  colors  the  flame  pale-green, 
and  fuses  at  about  four  to  a  black  magnetic  mass.  It  dissolves 
completely  in  the  fluxes,  giving  iron  and  manganese  reactions. 
It  is  soluble  in  nitric  and  hydrochloric  acids. 

The  name  eosphorite  is  from  the  Greek  rjGxrfyopos  (a  syno- 
nym of  </>ft)cr^)o/jo9,  whence  the  name  phosphorus),  which  means 
dawn-bearing,  in  allusion  to  the  characteristic  pink  color  of 
the  crystallized  mineral. 

2.  TKIPLOIDITE. 

Physical  characters. — Triploidite  occurs  in  crystalline  aggre- 
gates which  are  distinctly  parallel-fibrous  to  columnar  in  some 
cases,  and  in  others  divergent ;  and  again  confusedly  fibrous 
to  nearly  compact  massive.  Occasionally  individual  prismatic 
crystals  are  distinct,  being  separated  from  one  another  by  the 
transparent  quartz  in  which  they  are  imbedded  and  from 
which  they  become  detached  when  the  mass  is  broken  into  small 
fragments.  The  isolated  crystals  have  sometimes  a  length  of 
an  inch  or  more,  but  it  is  not  possible  to  detach  them  except 
in  very  small  pieces.  The  conditions  are  obviously  extremely 
unfavorable  to  the  formation  of  terminated  crystals,  but  a  care- 
ful and  long-continued  search  upon  a  large  amount  of  material 
was  at  last  rewarded  by  the  discovery  of  a  few  more  or  less 
perfect  specimens.  In  rare  instances  the  crystals  have  been 
observed  standing  free  in  small  cavities  in  the  massive  mineral. 
The  crystals  have  perfect  orthodiagonal  cleavage. 

The  hardness  of  triploidite  is  4.5-5,  and  the  specific  gravity 
3.697.  The  luster  is  vitreous  to  greasy-adamantine.  The 


58 


FIRST  BRANCHVILLE  PAPER. 


FIGURE  4. 


color  is  yellowish  to  reddish-brown,  in  the  distinct  crystals 
also  topaz-  to  wine-yellow,  and  occasionally  hyacinth-red.  The 
streak  is  nearly  white.  Transparent  to  translucent.  The  frac- 
ture is  subconchoidal. 

Crystalline  form.  —  Of  the  few  terminated 
crystals  obtained,  three  only  were  suitable 
for  measurement  and  only  one  of  these  had 
the  terminations  complete.  These  were  ex- 
tremely small,  but  the  planes  were  of  so 
high  a  luster  that  they  gave  good  reflections, 
but  little  inferior  to  those  obtained  from  the 
best  eosphorite  crystals.  The  planes  in  the 
prismatic  zone  are  in  the  larger  crystals  so 
much  striated  as  to  admit  of  no  satisfactory 
measurements.  In  the  crystals  selected  for 
careful  measurement  the  only  planes  in  this  zone  which  could 
not  be  used  at  all  were  the  clinopinacoids,  for  the  others  the 
reflections  were  reasonably  good.  The  crystals  show  occa- 
sionally false  planes,  bearing  no  relation  to  the  axes  of  the 
crystal,  and  which  are  evidently  impressions  of  portions  of 
adjoining  crystals. 

These  crystals  belong  to  the  MONOCLINIC  SYSTEM  and  their 
habit  is  shown  in  Figure  4.  The  axial  ratio  was  obtained  from 
the  following  fundamental  angles  : 

c  A  e  =  001  A  Oil  =  54°  48' 

a  A  m  =  100  A  110  =  60°  27' 
a  A  c   =  100  A  001  =  71°  46' 

These  angles  are  good,  though  a  little  less  so  than  those  given 
for  eosphorite  —  the  probable  error,  however,  does  not  exceed 
±  V.  The  axial  ratio  is : 

a  :  b  :  c  =  1.85715  :  1  :  1.49253;  £  =  71°  46' 
The  observed  planes  are : 


a,  100. 

b,  010. 


c,   001. 
m,  110. 


e,  Oil. 
P,  2H. 


FIRST  BRANCHVILLE  PAPER.  59 

A  comparison  of  the  angles  with  those  given  by  Brooke 
and  Miller  for  wagnerite  shows  that  the  two  species  are 
homoeomorphous. 

Thus,  in  the  three  diametral  zones,  we  have : 

Triploidite.  Wagnerite  (Miller). 

m  A  m,  110  A  1TO,  =  120°  54'  9^9   =  122°  25' 

c  A  a,  001  A  100,  =    71°  46'  c  A  a   =    71°  53' 

e  A  ef,  Oil  A  OT1,  =  109°  36'  e  A  e',  =  110°    6' 

As  the  crystal  of  wagnerite  is  placed  by  Miller,  the  planes  #, 
a,  c,  and  e  have  the  symbols  (120),  (100),  (001),  (021)  respec- 
tively. In  the  figure  given  by  Miller  the  prism  g  (120), 
corresponding  to  m  (110)  of  triploidite,  has  the  greatest 
development ;  it  was  made  the  unit  prism  by  Naumann. 

Optical  properties.  —  The  only  point  that  could  be  estab- 
lished in  regard  to  the  optical  character  of  triploidite  was  the 
position  of  the  axes  of  elasticity.  The  crystal  used  for 
measurement  had  the  clinopinacoid  so  far  developed  that  it 
could  be  examined  directly  in  a  Rosenbusch  microscope.  It 
was  found  that  of  the  two  axes  which  lie  in  the  plane  of 
symmetry,  one  very  nearly  coincides  with  the  vertical  axis, 
being  inclined  behind  (see  figure  4)  3° -4°,  and  the  other 
consequently  is  almost  normal  to  the  orthopinacoid.  The 
position  of  the  optic  axes  could  not  be  fixed.  The  crystals 
show  no  perceptible  absorption  phenomena. 

Chemical  composition.  —  Triploidite  was  analyzed  by  Mr. 
Penfield.  This  hydrous  phosphate  was  found  to  contain  iron 
and  manganese,  both  being  in  the  lowest  state  of  oxidation, 
with  a  small  amount  of  lime ;  it  is  entirely  free  from  fluorine. 
The  results  of  two  analyses  are  : 

Relative  number  of  atoms 
I.  II.  Mean.  calculated  from  the  mean. 

P206    32.14  32.08  32.11                     0.226    1.00     1 

FeO     15.07  14.69  14.88    0.207} 

MnO    48.35  48.55  48.45    0.682  [•     0.895    3.96    4 

CaO       0.36  0.29  0.33    0.006) 

H20       4.01  4.15  4.08                    0.226    1.00    1 

99.93  99.76  99.85 


60  FIEST  BRANCHVILLE  PAPER. 

The  ratio  P2O5 :  RO  :  H2O  =  1:4:1  corresponds  to  the 
formula  R4P2O9  +  H2O,  or  R3P2O8  +  H2RO2,  where  R  = 
Mn  :  Fe  =  3  :  1.  This  formula  requires: 

P205  31.91 
FeO  16.18 
MnO  47.86 
H20  4.05 
100.00 

Among  the  other  phosphates  and  arsenates  the  following 
seem  to  be  closely  related  to  triploidite  in  composition : 

Libethenite     Cu3P208  +  H2Cu02  Orthorhombic. 

Olivenite        Cu3(P2,As2)08  +  H2Cu02     Orthorhombic. 
Lazulite          A12P208  +  H6A1206  Monoclinic. 

None  of  these  species  has  any  relation  to  triploidite  in 
crystalline  form.  On  the  other  hand,  the  similarity  between 
the  angles  of  wagnerite  and  triploidite  has  already  been 
shown;  moreover,  the  composition  of  triplite  is  analogous  to 
that  of  wagnerite  and  for  these  reasons  a  relation  between 
triplite  and  triploidite  immediately  suggests  itself.  The  com- 
position of  these  minerals  is  : 

Wagiierite  Mg3P208  +  MgF2. 

Triplite  (Fe,  Mn)3P208  +  (Fe,  Mn)  F2. 

Triploidite  (Mn,  Fe)3P208  +  (Mn,  Fe)  (OH)2. 

It  should  be  stated  that  the  perfect  transparency  and  bril- 
liant luster  of  the  crystals  analyzed  prove  beyond  all  question 
that  the  absence  of  fluorine  and  the  presence  of  water  (deter- 
mined directly)  are  not  due  to  any  alteration.  The  fact  that 
all  the  bases  are  in  the  lower  state  of  oxidation  would  be 
confirmatory  evidence  were  it  needed.  The  conclusion  to 
which  we  are  led  is  this  —  that  in  the  compound  triploidite 
the  radical  hydroxyl  (OH)  plays  the  same  part  as  the  element 
fluorine,  the  molecule  R(OH)2  taking  the  place  of  the  RF2.* 

*  This  is  the  first  mention  made  of  the  isomorphous  relation  of  fluorine 
and  the  univalent  hydroxyl  radical,  a  relation  now  well  established,  which 
has  served  as  a  key  to  the  solution  of  many  complex  problems  in  mineral 
chemistry,  several  of  which  will  be  noted  in  this  volume.  —  EDITOR. 


FIRST  BRANCHVILLE  PAPER.  61 

Pyrognostics.  —  In  the  closed  tube  triploidite  gives  neutral 
water,  turns  black  and  becomes  magnetic.  Fuses  quietly  in 
the  naked  lamp  flame  and  B.  B.  in  the  forceps,  colors  the 
flame  green.  Dissolves  in  the  fluxes,  giving  reactions  for 
manganese  and  iron.  Soluble  in  acids. 

An  analysis  of  another  specimen  of  triploidite  gave  P2O5 
32.24,  FeO  18.65,  MnO  42.96,  CaO  not  determined,  H2O  4.09, 
quartz  1.09.  The  lime  was  accidentally  lost,  but  calculating 
from  the  amount  of  phosphoric  acid  retained  by  the  iron  it 
amounted  to  0.90  per  cent.  The  analysis  is  interesting  as 
showing  that  the  iron  and  manganese  vary  in  different  speci- 
mens, the  darker  colored  varieties  containing  the  most  iron. 

The  name  triploidite  given  to  this  species,  from  triplite,  and 
eZSo?  form,  indicates  its  resemblance  to  triplite  in  physical 
characters,  and  its  relation  in  chemical  composition. 

3.    DlCKINSONITE. 

Physical  characters.  —  Dickinsonite  occurs  most  commonly 
in  crystalline  masses,  which  have  a  distinctly  foliated,  almost 
micaceous,  structure.  It  is  also  lamellar-radiated  and  some- 
times stellated,  the  laminae  being  usually  more  or  less  curved. 
This  massive  variety  forms  the  gangue  in  which  crystals  of 
eosphorite  are  often  imbedded,  and  also  sometimes  triploidite. 
It  moreover  occurs  in  minute  scales  distributed  through  the 
massive  eosphorite  and  giving  it  a  green  color,  and  is  some- 
tunes  imbedded  in  the  rhodochrosite.  Minute  tabular  crystals 
are  rare ;  they  are  observed  implanted  upon  the  gangue,  and 
also  scattered  through  the  reddingite.  In  general  aspect  the 
mineral  resembles  some  varieties  of  chlorite  though  very  un- 
like in  its  brittleness. 

It  has  perfect  basal  cleavage.  The  hardness  is  3.5-4,  and 
the  specific  gravity  is  3.338-3.343.  Luster  vitreous,  on  the 
cleavage  face  somewhat  pearly.  The  color  of  the  purest  crys- 
tal is  oil-  to  olive-green,  in  the  massive  varieties  generally 
grass-green  though  sometimes  quite  dark ;  the  streak  is  nearly 
white.  Transparent  to  translucent,  the  crystals  being  per- 
fectly clear.  The  laminae  are  very  brittle  ;  fracture  uneven. 


62  FIRST  BRANCHVILLE  PAPER. 

Crystalline  form.  —  Distinct   crystals   of   dickinsonite    are 
not  often  found,  and  owing  to  the  extremely  brittle  character 
of  the  mineral,  it  is  only  in  very  rare  cases  that  they  can  be 
obtained  showing  more  than  the  basal 
plane.    The  crystallographic  data  which 
are  given  here  were  all  obtained  from 
two  crystals,  which,  though  extremely 
small   and  yielding  only  approximate 
angles,  yet  served  to  decide  all  the  es- 
sential points.     Other  less  perfect  crys- 

FlGURE   5.  „ 

tals  gave  confirmatory  results. 

Dickinsonite  crystallizes  in  the  MONOCLINIC  SYSTEM.  The 
The  axial  ratio  and  obliquity  were  obtained  from  the  follow- 
ing angles :  — 

Plane  angle  of  the  base  =  120°  0' 
c  A  a,     001  A  100     =     61°  30' 
c  A  a,     001  A  301     =     42°  30' 

The  axial  ratio  is :  — 

a  :  b  :  c  =  1.73205  :  1  :  1.19806 ;  ft  =  61°  30' 

The  observed  planes  are  as  follows : 

a,  100  c,    001  s,   221 

b,  010  p9   Til  x,  301 

The  accompanying  figure  shows  all  of  these  planes  except 
the  clinopinacoid,  which  was  only  once  observed. 

It  follows  from  the  table  of  angles,  here  omitted,  that  the 
angle  between  the  base  and  one  of  the  two  pyramids  (c  A  p  = 
61°  8')  differs  but  little  from  the  angle  between  the  base  and 
the  orthopinacoid  (c  A  a  =  61°  30') ;  there  are  thus  three 
planes  which  have  nearly  equal  inclinations  to  the  base. 
This  fact,  which  is  analogous  to  that  true  of  the  Vesuvian 
biotite  (meroxen),  as  pointed  out  by  Tschermak,  gives  to  the 
crystals  a  marked  rhombohedral  aspect  especially  as  the  planes 
x  (301)  and  s  (221)  have  usually  a  minor  development.  As 
exact  measurements  were  not  possible  the  true  relations  could 
hardly  be  established  beyond  doubt  until  recourse  was  had 


FIRST  BRANCHVILLE  PAPER.  63 

to  an  optical  examination.  This  showed  that  the  cleavage 
planes  are  not  isotrope  as  they  must  be  if  rhombohedral ;  on 
the  contrary  one  plane  of  vibration  is  exactly  parallel  to  the 
edge  c/a,  and  the  other  normal  to  it. 

The  rhombohedral  pseudo-symmetry  is  also  shown  in  the 
fact  that  the  plane  angle  of  the  base  differs  very  little  if  at 
all  from  120°.  The  most  careful  measurements  practicable 
failed  to  establish  any  variation.  That  the  angle  really  is 
120°  seems,  moreover,  to  be  indicated  by  the  fact  that  on 
many  cleavage  laminae  triangular  markings  are  visible,  which 
are  apparently  equilateral,  the  angles  measuring  60°;  other 
analogous  markings  have  four  or  five  sides  but  always  with 
angles  of  60°  or  120°,  as  near  as  the  measurements  can  be 
made. 

The  above  facts  show  that  crystallographically  dickinsonite 
is  related  to  the  micas  and  chlorites,  although  most  unlike 
them  chemically. 

The  plates  of  dickinsonite  are  sometimes  striated  parallel 
to  the  edges  c/p,  c/pf,  and  also  c/a,  corresponding  to  the 
triangular  markings  mentioned,  and  still  more  increasing  the 
rhombohedral  aspect  of  the  crystals.  No  twins  have  been 
observed,  although  some  very  imperfect  crystals  early  sug- 
gested their  possible  occurrence. 

The  cleavage  plates  show  a  marked  dichroism,  parallel  to 
the  edge  c/a,  the  rays  being  grass-green  and  much  absorbed 
and  normal  to  this  yellow-green.  No  examination  of  a  sec- 
tion perpendicular  to  the  cleavage  was  possible,  so  that  the 
position  of  the  axes  of  elasticity  in  the  plane  of  symmetry 
could  not  be  determined. 

Chemical  composition.  —  The  following  analysis  was  made 
by  Mr.  S.  L.  Penfield.  The  purest  material  available  was 
selected,  but  it  was  found  impossible  to  separate  it  entirely 
from  a  little  admixed  quartz  and  eosphorite.  The  small 
amount  of  alumina  present  is  assumed  to  belong  to  the 
eosphorite,  and  the  calculations  made  accordingly.  In  the 
table  below,  column  (I)  gives  the  original  analysis ;  (II)  gives 
the  amount  of  each  constituent  of  the  impurities  to  be  de- 


64 


FIRST  BRANCHVILLE  PAPER. 


ducted;  (III)  gives  the  remainder  after  this  deduction  has 
been  made,  and  (IV)  the  final  composition  after  being 
averaged  up  to  the  original  amount. 


P205 

A1208 

FeO 

MnO 

CaO 

Li20 

K20 

Na20 

H20 

Quartz 


II. 

Eosphorite  and 
quartz. 

2.13 
1.55 
0.50 
1.63 


100.25 


1.08 

3.30 

10.19 


III. 

35.36 

11.14 

22.55 

12.00 

0.03 

0.80 

4.71 

3.47 

J_L_1 

90.06 


IV. 

39.36 

12.40 

25.10 

13.36 

0.03 

0.89 

5.25 

3.86 

100.25 


The  ratio  calculated  from  analysis  (IV)  is  as  follows: 

P206  =0.277     0.277        1.00        4 

FeO    =0.172 

MnO  =  0.353 

CaO    =0.238 

Li20   =  0.001 

K20    =0.009 

Na20  =  0.085 

H20    =0.215 


3.09      12 


0.215        0.77 


The  ratio  P2O6  :  RO  :  H2O  =  4  :  12  :  3  corresponds  to  the 
formula  R3P2O8  +  |H2O.  If  R  =  Mn  :  Fe  :  Ca  :  Na  =  5  :  21  : 
3  :  1  J  ;  this  formula  requires  : 

P205  =40.05 
FeO  =12.69 
MnO  =  25.04 
CaO  =11.85 
Na20=  6.56 
H20  =  3.81 
100.00 


FIRST  BRANCHVILLE  PAPER. 


65 


This  corresponds  as  closely  as  could  be  expected  with  the 
analysis  (IV)  given  above. 

Another  analysis  by  Mr.  Penfield  on  a  separate  sample  of 
dickinsonite  is  given  below,  the  lime  having  been  lost  is 
determined  by  difference.  The  results  are  arranged  as  before : 
(I)  is  the  original  analysis;  (II)  the  amount  of  quartz  and 
eosphorite  present;  (III)  the  result  after  deducting  these, 
and  (IV)  the  final  result  calculated  again  to  100. 


II. 


Eosphorite  and 
quartz. 

P205 

38.18 

2.13 

A1208 

1.55 

1.55 

FeO 

11.36 

0.50 

MnO 

23.48 

1.63 

CaO 

[13.67] 

.  .  . 

Li20 

0.22 

.  .  . 

K20 

0.67 

.  .  . 

Na20 

4.36 

.  .  . 

H20 

4.62 

1.08 

Quartz 

1.89 

1.89 

III. 


36.05 


IV. 


39.53 


10.86 

11.90 

21.85 

23.96 

[13.67] 
0.22 

[14.98] 
0.24 

0.67 

0.73 

4.36 

4.78 

3.54 

3.88 

100.00 


8.78 


91.22 


100.00 


Pyrognostics.  —  In  the  closed  tube  gives  water,  the  first  por- 
tions of  which  react  neutral  to  test  paper,  but  the  last  portions 
are  faintly  acid.  The  residue  is  magnetic.  Fuses  in  the  naked 
lamp  flame,  and  B.  B.  in  the  forceps  colors  the  flame  at  first 
pale  green,  then  greenish  yellow.  Dissolves  in  fluxes  and 
affords  reactions  for  iron  and  manganese.  Soluble  in  acids. 

There  is  no  known  phosphate,  so  far  as  we  are  aware,  which 
bears  any  relation  to  dickinsonite  in  crystallographic  character, 
and  in  chemical  composition  it  seems  also  to  be  without  any 
very  near  relatives. 

We  have  named  this  most  interesting  mineral  dickinsonite  in 
honor  of  the  Rev.  John  Dickinson  of  Redding,  Conn.,  our 
obligations  to  whom  we  have  already  acknowledged. 


66  FIRST  BRANCHVILLE  PAPER. 

4.   LITHIOPHILITE. 

The  occurrence  of  this  mineral  in  the  deepest  explorations 
made  has  already  been  mentioned.  It  is  found  imbedded  in 
albite  in  irregular  rounded  masses  one  to  three  inches  in  diam- 
eter and  coated  with  a  black  mineral,  the  result  of  its  own  oxi- 
dation ;  some  of  these  masses  have  only  a  small  core  of  unaltered 
mineral. 

Physical  characters. — No  crystals  of  lithiophilite  were  found, 
although  some  of  the  imbedded  masses  have  in  external  form 
a  somewhat  crystalline  aspect.  There  are  three  distinct  cleav- 
ages :  one  quite  perfect,  always  observable  whenever  the  min- 
eral is  broken ;  a  second  nearly  perfect  at  right  angles  to  the 
first ;  and  a  third  interrupted,  which  is  prismatic,  having  an 
angle  of  128°-1300,  and  inclined  at  right  angles  to  the  first 
named  cleavage,  and  115° -116°  to  the  second.  The  similarity 
in  composition  between  this  species  and  triphylite  makes  it 
possible  to  identify  these  three  cleavages  with  those  shown  by 
Tschermak  to  belong  to  the  latter  mineral :  the  most  perfect 
cleavage  is  basal,  the  second  nearly  perfect  is  brachydiagonal, 
and  the  third  interrupted  cleavage  is  prismatic  (m  /\  m  =  133° 
in  triphylite,  Tschermak). 

The  hardness  is  about  4.5 ;  and  the  specific  gravity,  in  two 
trials,  3.424,  and  3.432.  The  color  of  the  unaltered  mineral 
is  generally  bright  salmon-color,  occasionally  honey-yellow,  — 
varying  to  yellowish-brown  and  in  rare  instances  to  umber- 
brown  ;  this  darker  color  is  probably  due  to  incipient  altera- 
tion. It  has  a  vitreous  to  resinous  luster,  and  is  generally 
translucent,  though  small  cleavage  fragments  are  occasionally 
perfectly  transparent.  Fracture  uneven  to  subconchoidal. 

Optical  properties.  —  The  optic  axes  in  lithiophilite  lie  in  the 
basal  section  or  plane  of  most  perfect  cleavage,  the  acute 
bisectrix  being  normal  to  the  brachypinacoid.  The  axial  angle 
is  very  large,  the  axes  being  partially  visible  in  the  extreme 
border  of  the  field  in  the  polariscope.  The  angle  could  not  be 
measured  satisfactorily  except  in  oil  (n  =  1.47) ;  the  results 
of  the  measurements  are  as  follows : 


FIRST  BEANCHVILLE  PAPER. 


67 


2Ra  =  74°  45'  for  red  rays. 
2Ha  =  79°  30'  for  blue  rays. 

The  dispersion  of  the  axes  is  strong,  v  >  p.  The  character 
of  the  double  refraction  is  positive.  The  three  axial  colors 
are  quite  distinct,  as  follows : 

For  vibrations  parallel  to  a   (that  is  a)  deep  pink. 

b   (that  is  c)  pale  greenish  yellow. 
C    (that  is  b)  faint  pink. 

Chemical  composition.  —  The  following  analyses  are  by  Mr. 
Horace  L.  Wells. 

Ratio. 

l.OO      1 


i. 

n. 

Mean. 

Quantivalents. 

P2O5 

44.83 

44.51 

44.67 

0.314 

0.314 

MnO 
FeO 

40.80 
3.99 

40.91 
4.04 

40.86 
4.02 

0.576 
0.056 

|  0.632 

Li20 
Na20 
H2O 
Si02 

8.72 
0.13 
0.77 
0.63 

8.55 
0.16 

0.87 
0.66 

8.63 
0.14 

0.82 
0.64 

0.288 
0.002 

|  0.290 

99.87 

99.70 

99.78 

e  ratio 

P206: 

ii          i 

RO:R: 

.0  = 

1:2: 

1  pro 

2.01 
0.93 


be  a  normal  phosphate  analogous  in  composition  to  triphylite. 
Its  formula  is  LiMnPO4  or  Li3PO4  +  Mn3P2O8.    This  formula 

requires : 

P205        45.22 

MnO        45.22 

Li20          9.56 

100.00 

The  mineral  lithiophilite  is  consequently  a  manganese  mem- 
ber  of  the   triphylite   group.     Mr.  Penfield  has   previously 

shown  that  the  true  formula  of  triphylite,  hitherto  doubtful, 

i  ii  i  ii 

is  R3PO4  +  R3P2O8*,  where  R  —  Li,  and  R  =  Fe  mostly,  also 

Mn.     His  conclusions  are   confirmed   by  the   results  of  Mr. 
Wells'  analysis  of  lithiophilite. 

Rammelsberg  found  (as  a  mean  of  four  analyses)  in  the 
Bodenmais  mineral  39.97  per  cent  FeO,  and  9.80  per  cent  MnO. 

*  Amer.  Jour.  Sci.,  1877,  vol.  13,  p.  425. 


68  FIRST  BRANCHVILLE  PAPER. 

Mr.  Penfield,  in  his  analysis  of  the  Graf  ton,  New  Hampshire, 
obtained  26.09  per  cent  of  FeO  and  18.17  per  cent  MnO.  The 
altered  triphylite  from  Norwich,  Mass.,  also  contains  a  con- 
siderable amount  of  manganese,  but  as  manganese-sesquioxide 
(22.59-24.70  per  cent) ;  the  unaltered  mineral  has  never 
been  analyzed.  These  facts  go  to  show  that  between  the  true 
triphylite  (the  iron-lithium  phosphate)  and  the  lithiophilite 
(the  manganese-lithium  phosphate)  a  number  '  of  different 
compounds  exist,  containing  varying  amounts  of  iron  and 
manganese,  as  is  true  in  many  other  analogous  cases  of  iso- 
morphous  groups  of  compounds.  It  is  probable,  however, 
that  to  all  varieties  of  the  two  minerals  belongs  the  general 
formula : 


R3P04  +  R3P208  or  RttPO 


Pyr agnostics.  —  In  the  closed  tube  gives  trace  of  moisture, 
turns  dark  brown  and  fuses,  but  does  not  become  magnetic. 
Fuses  in  the  naked  lamp-flame,  and  B.  B.,  gives  an  intense 
lithia-red  flame  streaked  with  pale  green  on  the  lower  edge. 
Dissolves  in  the  fluxes  giving  in  O.  F.  a  deep  amethystine 
bead,  and  in  R.  F.  a  faint  reaction  for  iron.  Soluble  in  acids. 

The  name  lithiophilite,  from  lithium  and  (j>i\a$,  friend,  may 
properly  be  given  to  this  species,  as  it  contains  a  very  high 
percentage  of  lithia. 

5.  REDDINGITE. 

Physical  characters.  — <Reddingite  occurs  sparingly  in  minute 
octahedral  crystals,  belonging  to  the  orthorhombic  system.  It 
is  also  found  more  generally  massive  with  granular  structure ; 
it  is  associated  with  dickinsonite,  and  sometimes  with  triploid- 
ite.  As  compared  with  the  other  species  which  have  been 
described  it  is  a  decidedly  rare  mineral.  The  massive  mineral 
shows  a  distinct  cleavage  in  one  plane,  the  crystallographic 
direction  of  which  could  not  be  ascertained  in  the  crystals 
owing  to  their  small  size. 

The  hardness  is  3-3.5;  and  the  specific  gravity  for  the  mineral 
analyzed,  containing  12  per  cent  quartz  is  3.04 ;  this  gives  on 


FIRST  BRANCHVILLE  PAPER.  .  69 

calculation  for  the  pure  mineral  3.102.  The  luster  is  vitreous 
to  sub-resinous  :  the  color  of  the  perfectly  unaltered  mineral  is 
pale  rose-pink  to  yellowish-white,  sometimes  with  a  tinge  of 
brown;  crystals  are  occasionally  coated  dark  reddish-brown 
from  surface  alteration  ;  the  streak  is  white.  Transparent  to 
translucent  ;  fracture  uneven  ;  brittle. 

Crystalline  form.  —  The  crystals  of 
reddingite  are  rare  and  occur  only  in 
cavities  in  the  massive  mineral.  They 
have  uniformly  an  octahedral  habit; 
sometimes  only  the  unit  pyramid  is 
present,  and  in  other  cases  a  second 
macrodiagonal  pyramid,  with  the  brachy- 
pinacoid,  as  shown  in  the  accompanying 
figure.  The  crystals  belong  to  the  ORTHOBHOMBIC  SYSTEM. 
The  fundamental  angles  are  as  follows: 

p*p',       lllATll=    76°  50' 
p*p",     HI  A  Til  =  110°  43' 

These  angles  are  only  tolerably  exact,  the  probable  error 
being  as  high  as  ±5'.  The  axial  ratio  calculated  from  the 
above  angles  is: 

a  :  b  :  c  =  0.8678  :  1  :  0.9485 

The  observed  planes  are  : 

ft,   010  p,   111  0,212 

Reddingite  is  closely  isomorphous  with  scorodite  and  stren- 
gite  ;  the  corresponding  pyramidal  angles  for  the  three  species 
are  as  follows  : 

Reddingite. 


lllATll=    76°  50'  77°    8'  78°  '22' 

111  A  1T1  =    65°  16'  65°  20'  64°  24' 

111  A  TT1  =  110°  43'  111°    6'  111°  30' 

The  axial  ratios  of  the  three  species  are  as  follows  : 

a.  b.  c. 

Keddingite   ....         0.8678         :  1        :        0.9485 

Scorodite  (vom  Bath)         0.8658         :  1         :         0.9541 

Strengite  (Nies)   .     .        0.8652        :  1        :        0.9823 


70 


FIRST  BRANCHVILLE  PAPER. 


The  relations  of  the  three  species  in  chemical  composition 
are  spoken  of  in  a  later  paragraph. 

Chemical  composition.  —  The  best  available  material  was 
used  in  the  analyses  by  Mr.  Horace  L.  Wells ;  it  was  free 
from  every  impurity  with  the  exception  of  the  quartz,  which 
was  so  intimately  intermixed  that  separation  was  impossible. 
The  presence  of  the  quartz,  however,  did  not  interfere  in  the 
least  with  the  accuracy  of  the  composition  finally  deduced. 
The  water  was  determined  directly. 
Two  analyses  gave : 

i. 

12.09 
30.17 
40.85 
4.88 
0.32 
0.70 
11.70 


Quartz 

PA 
MnO 

FeO 

Na20  (trace  Li20) 

CaO 

H20 


II. 

Mean. 

12.07 

12.08 

30.56 

30.37 

40.58 

40.71 

4.70 

4.79 

0.23 

0.27 

0.64 

0.68 

11.33 

11.51 

100.71 


100.11 


100.41 


Excluding  quartz,  the   mean   of   the   two   above   analyses 
gives : 


PA 

34.52 

0.243          0.243 

1.00 

MnO 

46.29 

0.652  1 

FeO 
Na20  (tr.  Li20) 

5.43 
0.31 

0.075 
0.005 

0.746 

3.07 

CaO 

0.78 

0.014. 

H20 

13.08 

0.727          0.727 

3.00 

100.41 


The  ratio  P2O5  :  RO  :  H2O  =  1:3:3,  corresponds  to  the 
formula  Mn8P2O8  4-  3  aq.,  which  requires  the  following  per- 
centage composition: 

PA  =  34.72 

MnO  =  52.08 

H20  =  13.20 

100.00 


FTRST  BRANCHVILLE  PAPER.  71 

It  is  interesting  to  note  here  that  the  same  formula  was 
deduced  by  M.  Debray*  for  an  artificial  salt  which  he  ob- 
tained in  brilliant  crystalline  grains  by  boiling  a  solution  of 
phosphoric  acid  in  excess  with  pure  manganese  carbonate. 
He  gives,  however,  no  description  of  the  form  of  the  crystals 
obtained. 

The  close  correspondence  of  reddingite  with  scorodite  and 
strengite  has  already  been  pointed  out ;  chemically  the  rela- 
tion is  not  so  close,  for  the  manganese  is  all  in  the  lowest 
state  of  oxidation  and  only  three  molecules  of  water  are  pres- 
ent. The  formulas  for  the  three  minerals  are  as  follows  : 

Reddingite  Mn8P208  +  3  aq. 

Scorodite  Fe2As208  4-  4  aq. 

Strengite  Fe2P208  +  4  aq. 

Pyrognostics.  —  On  heating  in  the  closed  tube,  whitens  at 
first,  then  turns  yellow  and  finally  brown,  *but  does  not  be- 
come magnetic.  In  the  forceps  fuses  in  the  naked  lamp 
flame  (F  =  2).  B.  B.  colors  the  flame  pale  green  and  fuses, 
easily  to  a  blackish-brown  non-magnetic  globule.  Dissolves 
in  the  fluxes  and  reacts  for  manganese  and  iron.  Soluble  in 
hydrochloric  and  nitric  acids. 

Reddingite  is  named  from  the  town  in  which  the  locality 
is  situated.  It  was  the  last  of  the  above  species  to  be  dis- 
covered, and  we  were  led  to  make  an  especial  search  for  it 
by  finding  black  octahedrons  implanted  upon  one  specimen 
which  were  obviously  pseudomorphs  and  which  could  not 
be  referred  to  any  known  species.  Another  specimen  ex- 
hibited pseudomorphs  of  the  same  species,  but  where  the 
alteration  was  not  so  far  advanced. 

*  Annales  de  Chiraie  et  de  Physique,  III,  Ixi,  433,  1861. 


SECOND   BRANCHVILLE   PAPER. 

BY  GEOEGE  J.  BRUSH  AND  EDWARD  S.   DANA. 
(From  Amer.  Jour.  Sci.,  1879,  vol.  17,  pp.  359-368). 

IN  the  preceding  pages  an  account  has  been  given  of  the  dis- 
covery of  a  new  mineral  locality  at  Branchville,  Fairfield 
County,  Connecticut,  including  descriptions  of  five  new  min- 
erals, all  manganesian  phosphates,  occurring  there.  During 
the  autumn  following  the  publication  of  our  article  we 
pushed  forward  our  explorations  at  the  locality  with  as  much 
vigor  as  possible,  and  with  tolerable  success.  We  were 
fortunate  in  finding  a  new  and  independent  deposit  of  the 
phosphates,  and  obtained  from  it  a  considerable  quantity  of 
eosphorite,  lithiophilite  and  a  little  triploidite,  and  with  them 
some  other  species  of  interest,  among  which  we  may  mention 
a  series  of  uranium  compounds.  The  detailed  description  of 
these  discoveries  we  shall  defer  until  a  third  paper.  In  the 
present  paper  we  propose  to  give  the  descriptions  of  the  two 
additional  new  species  we  have  identified;  one  of  these  we 
mentioned  in  our  last  paper  under  the  name  of  fairfieldite. 
We  add  also  the  results  of  a  new  analysis  of  reddingite,  and 
some  further  facts  in  regard  to  lithiophilite.  Both  of  the 
new  species  came  from  the  original  material,  removed  by 
Mr.  Fillow,  when  the  locality  was  first  opened. 

6.   FAIRFIELDITE. 

General  physical  characters.  —  Fairfieldite  occurs  usually 
in  massive  crystalline  aggregates ;  also  rarely  in  distinct  crys- 
tals. The  structure  is  foliated  to  lamellar,  some  varieties 
closely  resembling  selenite;  also  occasionally  in  radiating 
masses  consisting  of  curved  foliated  or  fibrous  aggregations; 
these  radiated  forms  are  not  unlike  stilbite. 


SECOND  BRANCHVILLE  PAPER. 


73 


The  hardness  is  3.5,  and  the  specific  gravity  3.15.  The 
luster  is  pearly  to  sub-adamantine ;  on  the  surface  of  perfect 
cleavage  (£)  it  is  highly  brilliant.  The  color  is  white  to  pale 
straw-yellow ;  the  streak  is  white.  Transparent.  Brittle. 

Two  rather  distinct  varieties  have  been  observed :  the  first 
(A)  occurs  filling  cavities  in  the  reddingite,  and  covering 
the  distinct  crystals  of  this  mineral.  It  is  uniformly  clear  and 
transparent,  and  is  highly  lustrous,  showing  entire  absence 
of  even  incipient  alteration.  It  is  generally  foliated  to  lamel- 
lar, although  sometimes  of  a  somewhat  radiated  structure. 
The  second  variety  (B)  occurs  in  masses  of  considerable 
size  interpenetrated  rather  irregularly  with  quartz,  and  quite 
uniformly  run  through  with  thin  seams  and  lines  of  a  black 
manganesian  mineral  of  not  very  clearly  defined  character. 
This  mineral  is  granular  in  texture,  lustrous,  is  difficultly 
fusible,  and  consists  for  the  most  part  of  the  hydrated  oxides 
of  manganese  and  iron ;  but  contains  also  phosphoric  acid  and 
traces  of  lime. 

This  second  variety  of  fairfieldite  is  often  friable  to  the 
touch  and  lacks  something  of  the  brilliant  luster  of  the  first 
variety.  It  also  shows  greater  difference  of  structure,  pass- 
ing from  the  distinct  crystals  to  the  massive  and  radiated 
form.  The  identity  of  these  two  kinds  is  shown  by  the 
analyses  given  below.  Fairfieldite  also  occurs  in  small  par- 
ticles in  fillowite  (described  beyond),  and  hi  masses  of  some 
size  immediately  associated  with  eosphor- 
ite,  triploidite,  and  dickinsonite. 

Crystalline  form.  —  Indistinct  crystals 
of  fairfieldite  occur  occasionally  in  cavities 
in  the  massive  mineral.  They  are  usually 
composite  in  character,  made  up  of  many 
individual  crystals,  interpenetrating  each 
other,  and  in  only  an  approximately 
parallel  position.  On  the  most  favorable 
crystals  the  form  could  be  clearly  made 
out,  but  exact  measurements  were  quite 
impossible ;  this  is  the  more  to  be  regretted 


74  SECOND  BRANCHVILLE  PAPER. 

as  the  number  of  variable  elements  is  so  large.  The  cleavage 
parallel  to  b  (010)  is  highly  perfect;  that  parallel  to  a  (100) 
somewhat  less  so. 

The  crystals  belong  to  the  Tridinic  System,  and  the  general 
habit  is  shown  in  the  adjoining  figure.  The  following  supple- 
ment angles  were  accepted  as  the  basis  of  the  calculations. 

a  A  c  100  A  001  =    88° 

a  A  b  100  A  010  =  102° 

a^p  100  A  111  =    56°  30' 

c  *p  001  A  111=    78°  30' 

From  these  angles,  the  lengths  and  mutual  inclinations  of  the 
axes  were  calculated,  as  follows : 

a  :  b  :  c  =  0.2797  :  1  :  0.1976 ;  a  =  102°  9',  /?  =  94°  33', 
y  =  77°  20'. 

The  observed  planes  are  as  follows : 

a,   100  p,    111  s,    131  w,   230 

J,    010  q,   112  gt  320  o,    120 

c,    001  r,    113  m,  110  p,    1TO 

In  one  case  an  apparent  penetration-twin  was  observed,  the 
two  crystals  crossing  one  another  so  that  the  planes  b  and  a  of 
the  one  were  parallel  respectively  to  the  planes  a  and  b  of  the 
other.  If  this  coincidence  were  perfect  (exact  measurement 
was  out  of  the  question)  and  the  crystal  were  really  a  twin  the 
twinning-plane  must  make  with  a  (100)  an  angle  of  either  51° 
(toward  010)  or  39°  (toward  010).  This  condition  is  equally 
well  satisfied  by  the  plane  270  (100  A  270  =  51°  4'),  or  by  270 
(100  A  270  —  39°  3'.)  As  this  supposed  twinning-plane  has 
so  complex  a  relation  to  the  other  planes  of  the  crystal,  it  is 
probable  that  this  coincidence  is  only  accidental. 

Optical  properties.  —  Minute  fragments  of  fairfieldite  parallel 
to  the  two  cleavage  planes  were  examined  in  the  stauroscope, 
with  the  following  results  :  —  The  planes  of  light- vibration 
intersect  the  cleavage  plane  a  (100)  in  lines  which  make  angles 
of  40°  and  50°,  respectively,  with  the  edge  a  \  b.  One  optical 


SECOND  BRANCHVILLE  PAPER. 


75 


axis  was  visible  on  the  edge  of  the  field  in  converging  light, 
obviously  lying  in  the  vibration-plane  making  an  angle  of  50° 
with  the  obtuse  edge  named,  and  toward  that  edge. 

The  cleavage  plane  parallel  to  b  (010)  is  intersected  by  the 
vibration  planes  in  lines  making  angles  of  10°  and  80°  respec- 
tively with  the  edge  b  \  a.  In  this  case  also  an  optical  axis 
(the  second)  is  distinctly  visible  on  the  outer  limit  of  the  field. 
This  serves  to  fix  approximately  the  position  of  the  bisectrix. 
As  the  cleavage  fragments  examined  were  less  than  \  mm.  in 
size,  any  further  examination  was  impossible. 

Chemical  composition.  —  The  two  varieties  of  fairfieldite 
have  been  analyzed  by  Mr.  S.  L.  Penfield,  with  the  following 
results : 


PA 
FeO 
MnO 
CaO 


K20 
H20 

Quartz 


A. 

38.39 

5.62 

15.55 

28.85 

0.73 

0.13 

9.98 

1.31 

100.56 


B. 
39.62 

7.00 
12.40 
30.76 

0.30 

9.67 

0.55 

100.30 


The  ratios  of  the  oxides  calculated  from  these  analyses  are 
as  follows : 


A. 

P205 

0.270          0.270 

FeO 

0.078 

MnO 

0.219 

CaO 

0.515 

-      0.825 

Na0O 

0.012 

K26 

0.001 

H20 

0.554          0.554 

1.00 


3.06 


2.05 


0.279 
0.097 
0.175 
0.549 
0.005 

0.537 


B. 

0.279 


1.00 


0.826        2.96 


0.537        1.93 


The  ratio  P2O5  :  RO  :  H2O  =  1:3:2  answers  to  the  formula 
R3P2O8  +  2  aq.  If  here  R  =  Ca  :  Mn  +  Fe  =  2  :  1  and  the 
ratio  of  Mn  :  Fe  be  also  2:1,  the  formula  requires : 


76  SECOND  BRANCHVILLE  PAPER. 

P205  39.30 

FeO  6.64 

MnO  13.10 

CaO  30.99 

H2O  9.97 

100.00 

The  fact  that  the  second  variety  was  friable  and  somewhat 
deficient  in  luster  suggested  an  incipient  alteration,  but  the 
analysis  did  not  confirm  this  idea.  The  larger  amount  of  lime 
afforded  in  the  analysis  of  this  kind  is  possibly  due  to  admix- 
ture of  a  little  apatite,  which  is  often  observed  with  it,  and 
the  larger  proportion  of  iron  may  be  due  to  the  fact  that  this 
variety  could  not  be  entirely  freed  from  the  black  oxide  inter- 
penetrating it. 

Pyrognostics.  —  In  the  closed  tube  fairfieldite  gives  off 
neutral  water,  and  the  assay  turns  first  yellow,  then  dark 
brown,  and  becomes  magnetic.  In  the  forceps  glows,  blackens, 
and  fuses  quietly  at  about  4.5  to  a  dark  yellowish-brown  mass, 
coloring  the  flame  pale  green,  with  faint  reddish-yellow  streaks 
on  the  upper  edge.  Soluble  in  the  fluxes  giving  reactions  for 
iron  and  manganese.  Fairfieldite  is  soluble  in  nitric  and 
hydrochloric  acids. 

Fairfieldite  is  named  from  the  county  in  which  the  locality 
occurs. 

7.   FILLOWITE. 

General  physical  characters.  —  Fillowite  occurs  in  granular 
crystalline  masses.  By  fracture  the  crystalline  grains  can  be 
usually  separated  with  ease ;  they  show  in  most  cases  merely 
striated  planes  of  contact,  having  no  crystallographic  signifi- 
cance ;  occasionally,  however,  isolated  but  brilliant  crystalline 
planes  are  observed  and  rarely  a  nearly  complete  crystal.  The 
masses  are  not  infrequently  penetrated  by  distinct  prismatic 
crystals  of  triploidite ;  and  sometimes  they  enclose  particles  of 
fairfieldite.  The  outer  surfaces  are  very  often  coated  with  a 
silvery-white  radiated  mineral,  but  in  so  sparing  quantities 
that  we  have  been  thus  far  unable  to  determine  definitely 
its  character.  Reddingite  is  very  commonly  associated  with 


SECOND  BRANCHVILLE  PAPER.  77 

fillowite,  and  in  many  cases  it  is  not  easy  to  distinguish  the 
two  minerals. 

The  hardness  is  4.5,  and  the  specific  gravity  in  two  trials 
3.41  and  3.45.     The  luster  is  sub-resinous  to  greasy.     The 
color  generally  wax-yellow,  also  yellow- 
ish to  reddish-brown  with  a  red  or  green 
tinge,  and  rarely  almost  colorless.    Streak 
white.    Transparent  to  translucent ;  frac- 
ture uneven;  brittle. 

Crystalline  form.  —  The  crystals  of 
fillowite,  whose  occurrence  has  already 
been  mentioned,  have  a  marked  rhombo- 
hedral  aspect.  As  shown  in  the  figure 
the  three  pknes,  whose  several  inclinations  are  almost  identical, 
have  their  common  solid  angle  replaced  by  a  nearly  equi- 
lateral triangle.  The  measurements,  however,  point  to  a 
monoclinic  form,  and  that  this  is  the  true  explanation  is 
proved  by  the  optical  examination.  The  cleavage  is  basal, 
nearly  perfect. 

The  angles  accepted  as  the  basis  for  calculation  are  as 
follows : 

c  Aj9  001  A  Til  =58°  40' 

c  A  d  001  A  201  =  58°  31' 

p  *p  Til  ATT1  =95°  23' 

Calculated  from  these  the  elements  of  the  crystal  are : 
a  :  b  :  c  =  1.7303  :  1  :  1.4190 ;  /?  =  89°  51' 

The  position  taken  for  the  crystal  is  that  which  exhibits  most 
strikingly  its  close  approximation  to  the  rhombohedral  form. 
The  observed  planes  have  already  been  given ;  they  are : 

c,   001  d,   201  p,   Til 

Optical  properties.  —  It  was  found  possible  to  examine  small 
cleavage  fragments  of  fillowite  according  to  the  usual  methods, 
and  the  results  served  to  settle  the  question  of  the  system, 
which  the  measured  angles  might  have  left  undecided.  One 
vibration-plane  intersects  the  basal  plane  (cleavage)  parallel 


78 


SECOND  BRANCHVILLE  PAPER. 


to  the  edge  c  \  d  and  the  other  is  normal  to  it.  Moreover  the 
two  optic  axes  are  visible  when  the  Rosenbusch  microscope  is 
employed;  it  was  impossible  to  decide,  however,  in  which 
plane  they  lay,  since  the  only  sections  transparent  enough  for 
this  examination  were  destitute  of  the  other  crystalline  planes. 
Chemical  properties. — The  analyses  of  fillowite  by  Mr.  S. 
L.  Penfield  afforded  the  following  results : 


I. 

II. 

Mean. 

Ratios. 

P2o6 

39.06 

39.15 

39.10 

0.275           2.75 

1.00 

FeO 

9.48 

9.18 

9.33 

0.129 

MnO 

39.48 

39.36 

39.42 

0.555 

CaO 

undet. 

4.08 

4.08 

0.073 

8.51 

3.09 

Na20 

5.65 

5.84 

5.74 

0.092 

Li20 

0.07 

0.04 

0.06 

0.002  J 

H20 

1.75 

1.56 

1.66 

0.092           0.92 

0.33 

Quartz 

0.86 

0.90 

0.88 

100.11       100.27 


The  ratio  P2O5  :  HO  :  H2O  =  1  :  3  :  £,  corresponds  to  the 
+  H2O.     If  in  this  formula  R  =  Mn  :  Fe  : 


formula  3R3P2O{ 
Ca  :  Na  =  6  :  1 


1:1,  the  calculated  percentages  are: 


PA 
FeO 
MnO 
CaO 

Na20 
H20 


40.19 
6.80 

40.19 

5.28 

5.84 

1.70 

100.00 


The  very  small  amount  of  water  present  suggests  the  question 
as  to  whether  it  is  really  an  original  constituent  of  the  mineral. 
This  question  we  have  been  unable  to  decide  positively ;  we 
can  only  add  that,  of  a  large  number  of  specimens  examined, 
all,  even  the  most  transparent,  showed  its  presence.  Moreover, 
if  the  water  be  not  essential,  the  composition  of  the  mineral 
would  be  somewhat  analogous  to  triphylite,  containing 
sodium  instead  of  lithium,  and  the  want  of  correspondence  in 
crystalline  form  does  not  favor  this  idea. 

Pyrognostics.  —  In  the  closed  tube  fillowite  yields  a  small 
amount  of  water  which  reacts  neutral.     B.  B.  in  the  forceps 


SECOND  BRANCHVILLE  PAPER.  79 

colors  the  flame  momentarily  pale  green,  then  intensely  yellow 
and  fuses  with  intumescence  to  a  black  feebly  magnetic 
globule.  Fusibility,  1.5.  With  the  fluxes  reacts  for  iron  and 
manganese.  Soluble  in  nitric  and  hydrochloric  acids. 

We  have  named  this,  the  seventh  new  manganesian  phosphate 
from  this  locality,  after  Mr.  A.  N.  Fillow,  of  Branchville, 
Conn.,  our  obligations  to  whom  we  have  already  mentioned  in 
our  former  paper. 

REDDINGITE. 

In  our  preceding  paper  we  described  the  new  mineral 
reddingite,  and  showed  that  in  the  habit  of  its  octahedral 
crystals  and  in  their  angles  it  was  closely  homoeomorphous 
with  scorodite  and  strengite.  In  composition,  however,  it  was 
shown  that  there  was  a  variation,  as  follows :  — 

Scorodite  Fe2As203  -f-  4  aq. 

Strengite  Fe2P208  +  4  aq. 

Eeddingite  Mn3P208  +  3  aq. 

It  is  thus  seen  that  reddingite  differs  from  the  other  species  in 
that  the  metal  is  in  the  protoxide  condition,  and  again  since 
there  are  only  three  equivalents  of  water  present.  In  order  to 
establish  beyond  all  question  that  this  difference  was  a  real  one, 
we  have  had  a  second  analysis  made.  The  material  was 
selected  from  another  specimen,  and,  as  before,  was  obtained 
free  from  all  impurities  except  quartz. 

The  analyses,  made  by  Mr.  Horace  L.  Wells,  are  given 
below  (A)  as  also  that  by  him  (B)  published  in  our  preceding 
paper : 

A.  B. 

T  TT  Excluding 

quartz. 

P205  33.58  .  .  .  35.16  34.52 

FeO  7.54  .  .  .  7.89  5.43 

MnO  41.28  .  .  .  43.22  46.29 

CaO  0.67  .  .  .  0.71  0.78 

Na2O  trace  ...  ...  0.31 

HaO  11.72  11.72  12.27  13.08 

Quartz  4.46  4.39  J_1_L  .  .  . 

99.25  99.25  100.41 


80 


SECOND  BRANCHVILLE  PAPER. 


The  new  analysis  leads  to  the  formula  Mn8P2O8  +  3  aq.,  or 
the  same  as  that  obtained  before.  The  only  marked  difference 
between  the  two  results  is  one  which  we  have  found  to 
characterize  all  the  species  of  the  locality,  that  is,  a  little 
variation  in  the  relative  amounts  of  iron  and  manganese. 
That  the  manganese  is  really  in  the  protoxide  condition  cannot 
be  questioned  for  a  moment. 

Recapitulation. 

It  seems  of  some  interest  to  place  together  the  seven  new 
species  which  the  locality  has  afforded  us.  We  shall  hope, 
at  some  future  tune,  to  offer  some  remarks  in  regard  to  their 
mutual  relations ;  we  can  only  say  here  that  there  is  in  the 
facts  observed  nothing  to  suggest  that  any  one  of  the  species 
is  a  secondary  mineral  or  a  product  of  alteration;  all  seem 
to  be  original  minerals  of  the  vein.  We  have  found  single 
hand-specimens  which  exhibit  all  of  the  first  four  minerals 
together. 


1.  EOSPHORITE. 

R2A12P2010 .  4H20,       or 

2.  TRTPLOIDITE. 

R4P209 .  H20  or 

3.  DlCKINSONITE. 

4(R3P208)  -  3H20        or 

4.  LlTHIOPHILITE, 

LiMnP04  or 

5.  EEDDINGITE. 

K3P208 .  3H20  or 

6.  FAIRFIELDITE. 

K3P208 .  2H20  or 

7.  FlLLOWITE. 

3(E3P208).H20          or 


Orthorhombic. 
A12P208  +  2H2(Mn,Fe)02  +  2  aq. 

Monoclinic. 
(Mn,  Fe)3P208  +  (Mn,  Fe)(OH)2. 

Monoclinic. 
4(Mn,  Fe,  Ca,  Na2)3P208  +  3  aq. 

Orthorhombic. 
Li3P04  +  Mn3P208. 

Orthorhombic. 
(Mn,  Fe)8P208  +  3  aq. 

Triclinic. 
(Ca,  Mn,  Fe)3P208  +  2  aq. 

Monoclinic. 
3(Mn,  Fe,  Ca,  Na2)3P208  +  aq. 


THIRD  BRANCHVILLE  PAPER. 

BY  GEORGE  J.  BRUSH  AND  EDWARD  S.  DANA. 
(From  Amer.  Jour.  Sci.,  1879,  vol.  18,  pp.  45-50.) 

IN  the  present  paper  we  purpose  giving  an  account  of  the 
results  of  our  exploration  of  the  Branchville  locality  during 
the  past  year,  so  far  as  they  relate  to  the  manganesian 
phosphates.  In  our  preceding  papers  we  have  confined  our- 
selves almost  exclusively  to  the  original  body  of  phosphates 
exploited  by  Mr.  Fillow ;  we  having  mentioned  in  addition 
only  the  occurrence  of  a  single  small  deposit  of  lithiophilite. 
When  we  first  opened  the  locality,  our  hope  was  to  rediscover 
the  body  of  minerals  from  which  the  specimens  preserved  by 
Mr.  Fillow  had  been  obtained.  Our  success  in  this  was  quite 
indifferent ;  we  did,  indeed,  find  the  spot  aimed  at,  and  took 
from  it  a  small  quantity  of  the  minerals  in  which  we  were 
interested,  but  it  was  soon  clear  that  this  deposit  was  ex- 
hausted, and  we  must  look  farther  for  other  and  independent 
ones.  Having  but  little  to  guide  us  in  our  explorations,  we 
extended  them  quite  widely  in  the  seemingly  most  probable 
directions  and  expended,  in  time  and  money,  more  than  our 
final  success  would,  perhaps,  have  warranted.  We  discovered, 
however,  many  interesting  points  in  regard  to  the  minerals 
occurring  in  the  vein  as  a  whole,  which  we  intend  to  describe 
in  another  paper. 

Lithiophilite.  —  As  regards  the  phosphates,  the  mineral  lith- 
iophilite has  been  proved  to  exist  in  considerable  quantities. 
It  occurs  usually  not  in  large  deposits,  but  in  single,  isolated 
masses,  from  the  size  of  a  cherry  to  others  several  inches 
across.  The  method  of  occurrence  is  quite  uniform.  The 
masses  are  irregular  in  shape,  sometimes  rounded,  sometimes 
angular,  and  interpenetrating  the  associated  minerals  in  the 
most  intimate  manner.  These  associated  minerals  are  more 

6 


82  THIRD  BRANCHVILLE  PAPER. 

particularly  feldspar,  usually  albite,  and  spodumene.  The 
latter  mineral  is  very  generally  altered,  and  the  various 
products  of  its  alteration,  of  which  cymatolite  is  the  most 
common,  we  shall  describe  in  another  place.  The  lithiophilite, 
however,  though  often  coated  black  externally,  is  otherwise 
quite  free  from  alteration ;  the  only  exception  to  this  was  in 
the  case  of  that  first  discovered,  which  was  situated  near  the 
surface  of  the  ledge  and  was  much  oxidized.  It  will  be 
remembered  that,  in  what  we  have  alluded  to  as  the  original 
deposits  of  phosphates,  the  lithiophilite  occurred  very  spar- 
ingly and  only  as  an  occasional  nucleus  of  masses  of  the 
abundant  black  mineral,  the  product  of  its  alteration.  This 
is  described  in  our  preceding  paper,  and  analyses  of  these 
oxidation  products  are  there  given. 

The  lithiophilite  of  which  we  are  now  speaking  has,  in 
almost  all  cases,  the  salmon  color  of  that  first  described.  In 
one  specimen  the  amount  of  iron  was  determined  by  Mr. 
Penfield  and  found  to  be  but  3.56  per  cent.  The  lithiophilite 
sometimes  contains  imbedded  rhodochrosite.  Other  constantly 
associated  minerals  are :  apatite,  garnet,  uraninite  in  'brilliant 
black  octahedrons,  uranium  phosphates,  and  a  silicate  con- 
taining uranium,  near  cyrtolite,  all  of  which  will  be  described 
later. 

The  lithiophilite  was  the  only  mineral  of  the  manganesian 
phosphate  group  found  in  these  small  isolated  deposits.  A 
larger  mass  finally  reached,  however,  gave  us  another  variety 
of  this  mineral,  and  also  several  of  the  other  species.  This 
mass  was  of  so  peculiar  a  nature  as  to  deserve  a  somewhat 
minute  description.  It  afforded  first,  for  the  most  part,  only 
lithiophilite,  but  of  a  different  color  from  that  before  obtained, 
and  of  slightly  different  composition  as  shown  by  the  analysis 
given  beyond.  Closely  associated  with  the  lithiophilite  was 
a  considerable  amount  of  a  granular,  often  also  cellular, 
manganesian  carbonate,  rhodochrosite.  This  was  quite  im- 
pure, often  containing  interpenetrated  crystals  of  white  apatite, 
and  also  quartz.  With  the  lithiophilite  and  rhodochrosite, 
are  small  quantities  of  eosphorite  and  triploidite  and  traces 


THIRD  BRANCHVILLE  PAPER.  83 

of  dickinsonite ;  we  were  interested  in  finding  hand  specimens, 
showing  all  these  phosphates  together,  entirely  free  from 
alteration,  and  in  such  a  juxtaposition  as  to  seem  to  prove  a 
contemporaneous  origin.  Crystallized  out  in  cavities  in  the 
rhodochrosite  and  again  in  thin  seams  of  strings  through  it 
was  a  reddish-brown  mineral  which  proved  to  be  chabazite. 

Immediately  connected  with  the  minerals  described  was  a 
large  mass  of  a  green  chloritic  mineral,  of  which  we  took  out 
some  hundred  pounds.  Its  especial  interest  lay  in  the  inti- 
mate manner  in  which  it  was  associated  with  the  minerals  just 
mentioned.  This  is  particularly  true  of  the  eosphorite,  which 
was  scattered  irregularly  through  it  in  nodules  of  great  variety 
in  shape  and  size.  These  nodules  have  often  a  banded  coating 
of  a  firm  whitish  substance,  which  may  have  been  derived  from 
the  alteration  of  the  original  mineral,  and  which  entirely 
conceals  the  eosphorite  within. 

Having  given  this  general  description  of  the  method  of 
occurrence  of  these  minerals,  we  will  now  proceed  to  describe 
some  of  them  more  minutely. 

LITHIOPHILITE. 

We  have  already  stated  that  almost  all  of  the  lithiophilite 
discovered  was  similar  in  its  salmon  and  salmon-pink  color, 
and,  as  far  as  tested,  in  composition,  to  that  described  in  our 
first  paper ;  in  other  words,  it  contains  from  three  to  four  per 
cent  of  iron  protoxide.  The  lithiophilite,  associated  with  the 
green  chloritic  mineral,  has  a  light  clove-brown  color.  It  has 
a  brilliant  luster  and  is  clear  and  transparent.  The  specific 
gravity  is  3.482.  An  analysis  by  Mr.  S.  L.  Penfield  afforded 
the  following  results : 

Atomic  relation. 
P  ...  0.636 

Fe       0.180 ) 
Mn      0.451  ]   ~ 
Li        0.618 ) 
Na       0.010  J    " 


100.26 


I. 

II. 

Mean. 

P2O6 

45.22 

45.22 

45.22 

FeO 

13.10 

12.92 

13.01 

MnO 

31.93 

32.12 

32.02 

Li20 

9.26 

9.26 

Na20 

0.28 

0.30 

0.29 

H20 

0.17 

0.17 

Gangne 

0.31 

0.28 

0.29 

84  THIRD  BRANCHVILLE  PAPER. 

The  ratio  P  :  R  :  R  =  0.636  :  0.631  :  0.628  corresponds  very 
closely  with  the  formula  previously  accepted, 

RRP04  or  R3P04  +  K8P208. 

It  will  be  observed  that  the  amount  of  iron  in  this  variety  of 
the  mineral  is  considerably  greater  than  in  that  first  described 
and  alluded  to  above.  This  result  is  not  surprising,  and  indeed 
was  anticipated  from  the  color  of  the  specimen.  Mr.  Pen- 
field  has  brought  together  the  analyses  of  several  varieties  of 
triphylite  and  the  two  of  lithiophilite,*  and  thus  shows  the 
gradations  between  the  two  species.  The  one  extreme  is  the 
Bodenmais  triphylite  with  36.21  per  cent  FeO  and  8.96  per 
cent  MnO,  and  the  other  the  original  lithiophilite,  with  4.02 
per  cent  FeO,  and  40.86  per  cent  MnO.  The  relation  between 
these  two  minerals  is  closely  analogous  to  that  existing  between 
the  iron  and  manganese  carbonates,  siderite  (FeCO3),  and  rho- 
dochrosite  (MnCO3).  There  is  the  same  similarity  in  physical 
characters,  the  most  pronounced  difference  being  here  as  there 
in  the  color,  so  that  the  necessity  of  giving  the  two  minerals 
of  the  triphylite  group  distinct  names  cannot  be  questioned. 

EOSPHOKITE. 

The  eosphorite  we  have  spoken  of  as  forming  nodules  im- 
bedded in  the  massive  green  chloritic  mineral.  It  occurs  only 
massive,  but  shows  the  characteristic  cleavage  distinctly,  and 
is  clear  and  lustrous.  The  color  is  a  beautiful  pink,  sometimes 
quite  deep.  The  specific  gravity  is  3.11.  An  analysis  by  Mr. 
Horace  L.  Wells  gave  the  following  results : 

Ratio. 

PA  31.39  0.221             1.06 

A1208  21.34  0.208             1.00 

FeO  6.62  0.092 ) 

MnO  22.92  0.323  [•          2.12 

CaO  1.48  0.026 ) 

H20  15.28  0.849             4.04 

Insol.  1.46 
100.49 

*  Amer.  Jour.  Sci.,  1879,  vol.  17,  p.  226. 


THIRD  BRANCHVILLE  PAPER.  85 

The  ratio  of  P2O6 :  A12O3 :  RO  :  H2O  is  very  nearly  1:1:2:4, 
or  that  given  in  our  former  paper,  and  upon  which  the  formula 
was  based,  viz. : 

E2A12P2010 .  4H20  or  A12P208  +  2H2(Mn,  Fe)O2  +  2aq. 

The  third  Branchville  paper  concludes  with  descriptions, 
accompanied  by  analyses,  of  a  green  mineral  analogous  to 
chlorite,  and  of  chabazite  and  rhodochrosite. 


FOURTH     BRANCHVILLE     PAPER.  —  SPODUMENE 
AND   THE   RESULTS   OF  ITS   ALTERATION. 

BY  GEORGE  J.  BRUSH  AND  EDWARD  S.  DANA. 
(From  Amer.  Jour.  Sci.,  1880,  vol.  20,  pp.  257-284.) 

IN  the  present  paper  we  give  the  results  we  have  obtained 
in  a  study  of  the  spodumene  from  Branchville,  Conn.,  and  of 
the  various  minerals  derived  from  its  alterations.  It  is,  after 
the  feldspars,  mica,  and  quartz,  the  most  important  of  the  orig- 
inal minerals  of  the  locality,  and  occurs,  though  mostly  hi  an 
altered  condition,  in  very  large  quantities. 

A.  UNALTERED  SPODUMENE. 

The  greater  part  of  the  unaltered  spodumene  occurs  in 
confusedly  crystalline  masses,  showing  distinct  cleavage,  but 
seldom  any  approach  to  crystalline  form.  It  is  possible  to 
obtain  the  mineral  nearly  pure,  though  somewhat  intermingled 
with  albite,  in  blocks  weighing  several  hundred  pounds.  In 
this  form  the  spodumene  has  a  dull  white  color ;  it  is  in  many 
cases  somewhat  discolored,  and  is  only  partially  translucent; 
the  cleavage  surfaces  are  often  coated  with  delicate  dendrites 
of  manganese  oxide.  The  associated  minerals,  in  addition  to 
the  albite  and  a  little  quartz  and  mica,  are  apatite,  lithiophilite, 
columbite,  garnet,  and  uraninite,  with  various  other  uranium 
minerals  formed  from  alteration. 

In  addition  to  this  massive  variety,  the  spodumene  also 
occurs  in  an  unaltered  condition  as  nuclei  of  distinct 
pseudomorphous  crystals.  These  crystals  often  occur  of 
enormous  size,  imbedded  for  the  most  part  in  massive  quartz, 
though  sometimes  extending  into  the  albite.  The  nucleus  of 
spodumene  (see  below  and  figures  la,  5,  8,  14,  of  the  accom- 


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DESCRIPTION  OF  PLATE. 

In  the  figures  the  letters  employed  have  the  following  signification:  —  a  = 
albite,  though  here  it  is  to  be  remembered  that  (as  remarked  earlier)  most  of 
the  albite  contains  scales  of  muscovite,  and  hence  shades  into  cymatolite ;  c  = 
cymatolite ;  g  =  muscovite  ;  k  —  killinite ;  m  =  microcline  ;  s  =  spodumene  ; 
ft  =  &  spodumene. 

la,  16,  Ic :  Three  sections  across  a  single  crystal,  15  inches  wide  and  4£ 
long,  at  intervals  of  about  5  inches,  la,  from  near  the  terminated  extremity, 
consists  principally  of  ft  spodumene  (ft),  with  cymatolite  (c)  along  the  edges, 
and  a  little  glassy  spodumene  (s)  on  the  lower  side.  U  shows  only  ft 
spodumene  and  cymatolite,  the  latter  occupying  a  larger  portion  than  in  la. 
Ic,  from  the  lower  extremity  of  the  crystal  shows  cymatolite  only. 

2.  Section  across  a  crystal,  4^  inches  wide,  now  entirely  altered  to  cymatolite 
The  intricate  wavy  structure  of  this  mineral  is  shown,  as  also  the  tendency  of 
the  fibers  to  be  at  right  angles  to  the  edges. 

3.  Partial  section  taken  longitudinally ;   the  central   portion  consists  of 
finely  granular  albite   (a),  with  lines  of  coarsely  granular,   and   cleavable 
microcline  (m) ;  the  exterior  is  cymatolite  (c). 

4.  Fragment    of    a  crystal    showing   the    granular    albite   (a)   inclosing 
microcline  (m). 

5.  Section  across  a  large  crystal ;  the  exterior  fractured  and  irregular.     It 
consists  mostly  of  clear  pink  spodumene  (s)  with  bands  of  ft  spodumene  (ft) 
passing   through  it,  following  the   directions   of    the   cleavage ;   also   some 
cymatolite  (c)  on  the  exterior. 

6.  Consists  of  granular  albite  (a),  and  cymatolite  (c),  also  some  plates  of 
mica  (g). 

7.  Section  across  a  large  crystal  (natural  size),  the  interior  consisting  of 
fibrous  albite  (a)  and  the  exterior  cymatolite  (c). 

8.  Section  showing  some  of  the  original  spodumene  (s)  in  detached  points, 
with  cymatolite  (c)  radiating  from  them,  also  some  ft  spodumene,  granular 
albite  (a),  and  a  few  plates  of  mica  (g). 

9.  A  fragment  consisting  of  killinite  (k)  with  narrow  bands  of  cymatolite 
(c)  following  approximately  the  original  cleavage  directions  of  the  spodumene. 

10.  Section  across  a  large  crystal  (7$  inches  wide),  consisting  of  albite  (a) 
and  granular  microcline  (m). 

11.  13.   Fragments  showing  granular  albite  (a)  and  imbedded  in  it  broad 
cleavage  plates  of  microcline  ;  in  each  crystal  these  plates  are  all  in  parallel 
direction. 

12.  Fragment  of  a  crystal,  showing  ft  spodumene  (ft)  inclosed  in  albite  (a), 
the  exterior  portion  consisting  of  killinite. 

14.  Portion  of  a  crystal  with  the  spodumene  (s)  cymatolite  (c)  radiating 
from  it,  and  granular  albite  (a) ;  one  band  through  the  spodumene  is  still  ft 
spodumene. 


PLATE 


fe^ 


iti^flM^^^w^ 


^ 


Photo    Lith.   E.  Crisand,   New  Haven,  Ct. 


PSEUDOMORPHS  AFTER  SPODUMENE 


FOURTH  BRANCHVILLE  PAPER.  87 

panying  plate  *)  is  in  every  case  sharply  separated  from  the 
altered  mineral  surrounding  it,  and  its  characters  show  that 
the  crystals  must  originally  have  had  rare  beauty.  One  of 
the  finest  crystals  that  we  have  found  thus  far  had,  as  imbedded 
in  the  quartz,  a  length  of  three  feet,  a  width  of  eight  inches 
and  a  thickness  of  two  inches.  The  unaltered  spodumene,  of 
a  fine  amethystine  color,  made  up  about  one-fourth  of  the 
whole,  extending  rather  regularly  through  the  middle  of  the 
crystal.  Unfortunately,  the  spodumene  was  much  rifted  and 
fractured,  so  that  its  former  transparency  had,  for  the  most 
part,  disappeared.  The  exterior  of  the  crystal  consisted 
principally  of  0  spodumene,  with  small  quantities  of  cymatolite 
and  albite.  Another  altered  crystal  was  measured  while 
imbedded  in  the  quartz,  of  which  a  length  of  over  four  feet 
was  exposed.  It  is  not  possible  to  extract  these  crystals 
entire,  but  many  fragments  have  been  obtained  which  have  a 
width  of  over  a  foot  across  the  prism  and  a  thickness  of  two 
to  four  inches.  In  habit  the  crystals  are  much  like  those  from 
Norwich,  Massachusetts.  They  are  generally  broad  or  flat, 
through  the  development  of  the  orthopinacoid,  and  compara- 
tively thin ;  not  unfrequently  they  are  well  terminated. 
Occasional  stout  crystals,  having  a  square  prismatic  form, 
much  like  pyroxene,  are  also  observed. 

In  the  better  specimens  the  spodumene  is  perfectly 
transparent,  sometimes  colorless,  and  again  of  a  beautiful 
rose-pink  or  amethystine-purple  color.  It  shows  the  prismatic 
cleavage  with  unusual  perfection,  and  that  of  the  clinopinacoid 
irregularly.  The  angle  of  the  prismatic  cleavage  —  viz., 
87°  13' —  was  obtained  with  great  exactness. 

Chemical  composition.  —  An  analysis  of  the  transparent  pink 
spodumene  was  made  by  Mr.  S.  L.  Penfield  with  the  following 
results.  Specific  gravity  =  3.193. 

*  Figures  1  to  14  inclusive  are  to  be  found  on  the  accompanying  plate,  the 
other  figures  (15-20)  are  in  the  text. 


FOURTH  BRANCHVILLE  PAPER. 


I. 

II. 

Mean. 

Si02 

64.32 

64.18 

64.25 

A1203 

27.14 

27.26 

27.20 

0.262  ) 

Fe20 

0.18 

0.22 

0.20 

0.001  ] 

Li20 

7.64 

7.59 

7.62 

0.254  ) 

Na20 

0.39 

0.39 

0.39 

0.006) 

K2O 

tr. 

tr. 

tr. 

Ignition 

0.24 

0.24 

0.24 

99.91 

99.88 

99.90 

Eatio. 

1.071  4.00 

0.263  0.98 

0.260  0.97 


The  ratio  of  Li2O  :  A12O3  :  SiO2  —  1:1:4;  this  corresponds 
to  the  oxygen  ratio*  of  1:3:8.  The  formula  is  then, 
neglecting  the  very  small  amount  of  soda, 

Li3Al2Si4Oi3. 

This  result  agrees  exactly  with  that  reached  by  Doelter  in  his 
investigation  of  the  composition  of  spodumene,f  and  with  that 
of  Julien.J  It  is  to  be  noted,  however,  that  the  percentage  of 
lithia  here  obtained  is  higher  and  that  of  soda  lower  than  in 
any  analyses  previously  published.  For  example,  Dcelter 
found  in  the  Norwich  mineral  7.04  Li2O,  1.10  Na2O  and  0.12 
K2O  ;  in  that  from  Brazil  7.09  Li2O  and  0.98  Na2O.  Julien 
obtained  in  the  Goshen  spodumene  6.89  Li2O,  0.99  Na2O,  1.45 
K2O  ;  and  in  that  from  Chesterfield  6.99  Li2O,  0.50  Na2O,  and 
1.33  K2O.  Doelter  concludes  for  the  Norwich  mineral  that  the 
amount  of  lithia  obtained  is  rather  too  small  than  too  large, 
and  attributes  the  soda  present  to  incipient  alteration.  The 
correctness  of  this  view  seems  to  be  proved  by  the  analyses 
here  published  of  the  B ranch ville  mineral,  which  certainly 
left  nothing  to  be  desired  in  regard  to  purity  or  freedom  from 
alteration.  The  great  tendency  of  spodumene  to  change  by 
the  assumption  of  potash  or  soda  and  loss  of  lithia  will  be 
made  evident  by  what  follows. 

B.   ALTERATION  OF  SPODUMENE. 

As  the  result  of  the  alteration  of  the  spodumene,  we  have 
found  two  substances  which  at  first  sight  seem  to  be 

*  This  ratio  was  obtained  by  Brush  from  analyses  of  the  Massachusetts 
mineral  in  1850.  See  page  30. 

t  Tschermak,  Min.  u.  Petr.  Mitth.,  i,  517,  1878. 

$  Annals  of  the  New  York  Acad.  of  Sci.,  vol.  i,  No.  10. 


FOURTH  BRANCHVILLE  PAPER.  89 

homogeneous,  and  each  of  which  has  a  definite  chemical 
composition,  and  which,  notwithstanding,  are  only  intimate 
mechanical  mixtures  of  two  species ;  one  of  these,  called  by  us 
fi  spodumene,  is  made  up  of  albite  and  a  new  lithia  mineral  to 
which  we  have  given  the  name  eucryptite;  and  the  other  is 
cymatolite,  an  aggregate  of  albite  and  muscovite.  We  have 
also  found  the  following  independent  minerals :  —  albite, 
microcline,  muscovite,  and  killinite.  The  two  complex  sub- 
stances and  all  of  the  last  named  minerals,  except  the  mica, 
occur  as  distinct  pseudomorphs,  having  the  form  of  the 
spodumene.  The  mica,  taken  independently  of  its  constant 
associate  the  albite,  plays  only  a  secondary  part.  In  addition 
there  are  other  pseudomorphs,  of  composite  character, 
consisting,  as  Mr.  Julien  has  well  expressed  it,  "  of  vein 
granite." 

We  will  first  give  the  physical  and  chemical  characters  of 
the  various  minerals  (including  the  two  aggregates)  taken 
separately,  and  then  go  on  to  describe  more  minutely  the  way 
in  which  they  are  associated  together. 

I.   PRODUCTS  OF  THE  ALTERATION. 
1.   /3  Spodumene. 

The  substance  which  we  have,  for  convenience,  called  fi 
spodumene,  since  we  do  not  regard  it  as  deserving  an  inde- 
pendent name,  seems  to  mark  the  first  step  in  the  alteration  of 
the  spodumene. 

Physical  characters.  —  It  is  a  compact,  apparently  homo- 
geneous mineral,  having  a  rather  indistinct  fibrous  to  columnar 
structure,  this  being  always  at  right  angles  to  the  adjoining 
surface  of  the  original  mineral.  Hardness  5.5  to  6;  specific 
gravity  2.644-2.649.  Color  white  to  milk-white,  and  again 
slightly  greenish-white  ;  translucent.  Fusibility  =  2.25. 

Chemical  composition.  —  Analyses  of  three  independent 
specimens  have  been  made  by  Mr.  S.  L.  Penfield.  Number  1 
was  taken  from  a  crystal,  part  of  which  consisted  of  the 
transparent  pink  spodumene,  described  above,  and  the  outer 


90 


FOURTH  BRANCHVILLE  PAPER. 


portion  was  this  mineral  (similar  to  Figure  5).  The  line  of 
demarcation  was  perfectly  sharp,  so  that  the  purity  of  the 
material  analyzed  cannot  be  questioned.  The  results  of  the 
analysis  are  as  follows : 


No.  I,  G.  =  2.649. 

I. 

Si02 

61.35 

A1203 

26.26 

Fe203 

0.24 

Li20 

3.63 

Na20 

8.32 

K20 

tr. 

Ignition 

0.46 

100.26 


II. 

61.42 

25.74 

0.24 

3.59 

8.25 

tr. 

0.46 

99.70 


Mean. 

61.38 

26.00 

0.24 

3.61 

8.29 

tr. 

0.46 

99.98 


0.253  ) 
0.002  } 
0.120 
0.134 


Ratio. 
1.023 

0.255 


4.00 
0.99 


0.254        0.99 


The  second  portion  analyzed  was  from  a  fragment  of  a  large 
and  entirely  altered  crystal ;  its  dimensions  were  9  by  8  by  2  \ 
inches.  It  consisted  mostly  of  cymatolite,  and  the  /3  spodu- 
mene  had  all  the  appearance  of  passing  insensibly  into  it ; 
a  single  fragment,  across  the  prism,  could  be  obtained  made 
up  of  both  minerals,  the  fibrous  structure  of  the  one  being 
continued  in  the  other  (similar  to  Figure  16).  The  analysis 
yielded : 


No.  2,  G.  =  2.644.             I. 

II. 

Mean. 

Ratio. 

Si02 

61.46 

61.57 

61.51 

1.025 

4.00 

A1208 

[not  determined] 

26.56 

26.56 

0.258 

1.01 

Li20 

3.55 

3.44 

3.50 

0.117) 

Na2O 

8.15 

8.13 

8.14 

0.131  > 

0.249 

0.97 

K2O 

0.15 

0.15 

0.15 

0.001  ) 

Ignition 

0.29 

0.29 

0.29 

100.14      100.15 

The  third  portion  was  part  of  a  smaller  and  well  developed 
crystal,  having  the  external  prismatic  form  complete.  It  con- 
sisted in  the  interior  of  spodumene,  then  the  /3  spodumerie 
making  up  the  greater  part  of  the  whole,  and  finally  a  thin 
crust  of  cymatolite.  The  specimen  analyzed  was,  as  far  as 
the  eye  could  detect,  perfectly  pure  and  homogeneous.  The 
color  was  greenish-white  and  it  was  decidedly  translucent. 
The  analysis  afforded: 


FOURTH  BRANCHVILLE  PAPER.  91 

No.  3,  G.  =  2.649.  I.                   II.  Mean.                                       Ratio. 

SiO2  61.78          61.64  61.71                               1.028        4.00 

A12O3  26.57          26.69  26.63                              0.259         1.01 

Li20  3.83  3.83        0.128) 

Na20  8.16  8.16        0.132  f 

K2O  tr.  tr. 

Ignition  _0.21  0.21 

100^53  100.54 

If  the  mean  analyses  of  the  three  groups  be  compared,  it 
will  be  found  that  they  agree  very  closely  with  one  another ; 
in  fact  the  agreement  is  as  close  as  could  be  expected  for 
three  successive  analyses  made  upon  the  same  material.  But, 
as  will  be  seen  from  what  has  already  been  said,  the  three 
samples  were  entirely  independent,  being  taken  from  different 
parts  of  the  ledge  and  differing  in  manner  of  association ;  the 
agreement  between  them  thus  becomes  very  striking.  The 
ratio  obtained  for  each, 

R20  :  R203  :  Si02  =  1:1:4, 

is  the  same  as  that  of  spodumene,  from  which  it  differs  only 
in  this :  that  one-half  of  the  lithium  has  been  removed  and 
its  place  (chemical  equivalent)  taken  by  sodium.  The  form- 
ula is  then : 

(Li,  Na)2Al2Si4012  =  Li2Al2Si4012  +  Na2Al2Si4O12  (1) 

or  =  Li2Al2Si208  +  Ka2Al2Si6016  (2) 

It  is  shown  below  that  the  formula  given  in  (2)  is  the  cor- 
rect one. 

The  facts  stated  thus  far  would  seem  to  be  sufficient  to 
prove  that  the  mineral  was  homogeneous  and  had  a  definite 
composition ;  there  are,  however,  other  facts  which  have  an 
important  bearing  upon  this  point. 

It  was  found  by  Mr.  Penfield  that,  although  the  mineral 
gelatinizes  with  acid,  it  is  not  entirely  decomposed.  On  the 
contrary,  it  is  divided  into  two  portions  by  the  treatment 
with  hydrochloric  acid,  viz.:  —  a  soluble  portion  (A),  and  an 
insoluble  remainder  (B),  the  latter  including  also  the  silica 


92  FOURTH  BRANCHVILLE  PAPER. 

extracted  from   the    soluble    part.      The    results    of    three 
analyses  gave 

A.   Soluble  in  HC1.  B"  H  lj  with 


No.  1  (17.97)  82.03  =  100,00 

"    2  16.65  83.01  =    99.66 

"    3  17.91  82.18  =  100.09 

In  the  case  of  No.  2,  complete  analyses  of  both  the  soluble 
and  insoluble  portions  were  made;  these  were  independent 
of  the  total  analyses  of  the  same  sample  already  given.  The 
method  of  analysis  was,  briefly,  as  follows  :  —  A  gram  of  the 
mineral  was  digested  with  HC1,  evaporated  to  dryness,  then 
moistened  with  HC1  and  a  second  time  evaporated  to  dryness. 
After  being  again  moistened  with  HC1  the  soluble  portion, 
A  above,  was  filtered  off  and  the  alumina  and  alkalies  deter- 
mined in  it  by  the  usual  methods.  The  insoluble  portion, 
which  included  the  silica  extracted  from  A,  after  being 
weighed  was  boiled  with  Na2CO3  and  (in  the  case  of  No.  3) 
with  a  little  KOH.  By  this  means  the  soluble  silica  of  A 
was  dissolved  out  and  the  insoluble  remainder  being  weighed, 
the  amount  of  the  soluble  silica  was  determined  by  the  dif- 
ference. Finally,  the  insoluble  part  was  analyzed  in  full  by 
the  usual  methods.  The  results  of  the  analyses  were  as 
follows  : 

No.  2. 

B.  Insoluble  in  HC1  with  silica  of  A  83.01 

Insoluble  remainder  after  treatment  with  soda  67.56 

15.45 
A.  Soluble  in  HC1  (16.65),  plus  silica  extracted  by  soda  from  B  32.10 

The  two  parts,  therefore,  into  which  the  original  mineral 
is  divided  by  hydrochloric  acid,  are  :  — 

No.  2. 

A.  Soluble  portion  32.10 

B.  Insoluble  portion  67.56 

99.66 

The  composition  obtained  for  A  was  as  follows  : 


FOURTH  BRANCHVILLE  PAPER. 


A.   Soluble  portion. 


Si02 
Al20a 
Li20 
K20 


No.  2. 

15.45 

13.00 

3.50 

0.15 

32.10 


Calculated  to  100. 
No.  2. 

48.13 

40.50 

10.90 

0.47 


Calculated  from 
formula. 

47.51 
40.61 
11.88 


100.00 


100.00 


For  the  above  analysis  the  ratio  is,  nearly : 
Si02  :  A1203  :  Li20  =2  :  1  :  1. 

This  corresponds  to  the  formula,  Li2Al2Si2O8,  the  percentage 
composition  of  which,  given  above,  agrees  well  with  the 
analysis. 

The  composition  obtained  for  B  was : 


B.    Insoluble  portion. 


Si02 

A1208 

Na20 


No.  2. 

46.06 

13.56 

7.94 

67.56 


Calculated  to  100. 
No.  2. 

68.18 
20.07 
11.75 


Calculated  from 
formula. 

68.62 
19.56 
11.82 


100.00 


100.00 


The  ratio  calculated  from  the  preceding  analysis  is : 
Si02  :  A1203  :  Na20  =  6.00  :  1.07  :  1.00. 

This  ratio  is  very  closely  that  of  albite,  viz. :  6  :  1  :  1,  so  that 
the  formula  for  the  insoluble  portion  is  Na2Al2  Si6Oi6. 

An  analysis  was  also  made  of  sample  No.  3,  but  the  sepa- 
ration was  a  little  less  complete  than  of  No.  2 ;  the  first 
digestion  in  acid  left  behind  a  very  little  of  the  soluble  min- 
eral, as  shown  by  the  presence  of  lithia  in  B,  and  then  in  the 
subsequent  treatment  of  the  insoluble  part  (in  which  also 
KOH  was  employed)  there  seemed  to  have  been  a  slight 
decomposition  of  the  albite.  The  results,  although  for  the 
reason  given  hardly  worth  putting  on  record,  were  satis- 
factory in  this,  that  they  confirmed  those  of  No.  2. 


94  FOURTH  BRANCHVILLE  PAPER. 

The  point  thus  far  established  may  be  stated  as  follows : 
A  chemical  examination  proves  that  the  substance,  called 
provisionally  /3  spodumene,  is  not  a  distinct  species,  but  only 
a  very  uniform  mixture  of  two  minerals ;  one  of  these,  called 
by  us  eucryptite,  dissolves  with  gelatinization  in  hydrochloric 
acid,  and  has  the  composition,  Li2Al2Si2O8;  the  other,  not 
attacked  by  acid,  is  albite,  Na2Al2Si6Oi6.  The  true  expression 
of  the  chemical  composition  of  the  substance,  is,  therefore, 
seen  to  be  that  (2)  given  above.  That  the  mixture  is  truly 
mechanical,  and  not  a  molecular  one  broken  up  by  the  acid 
(if  that  were  possible),  is  proved  by  this  significant  fact:  the 
insoluble  residue  (B  above),  left  after  the  digestion  in  sodium 
carbonate,  was  in  one  case  examined  under  the  microscope, 
and  found  to  be  crystalline,  and  to  have  the  peculiar  semi- 
fibrous  structure  belonging  to  the  pseudomorphous  albite,  as 
described  below. 

The  microscopic  examination  of  thin  sections  of  /3  spodu- 
mene confirms  the  results  reached  from  the  chemical  side  as 
to  the  complex  nature  of  the  substance,  and  gives,  in  addition, 
a  very  satisfactory  determination  of  the  crystalline  character 
of  the  new  lithia  mineral.  A  series  of  thin  sections  were 
prepared,  some  parallel  to  the  fibrous  structure,  that  is  at 
right  angles  to  the  original  mineral  (spodumene),  and  others 
transverse  to  the  fibers  and  consequently  parallel  to  the 
original  prism.  The  sections  parallel  to  the  fibers,  when 
examined  under  the  microscope,  seemed  at  first  sight  to  give 
no  proof  of  want  of  homogeneity.  The  fibers,  seemingly  of 
rounded  form  and  generally  parallel,  are  yet  quite  wavy  in 
outline,  and  are  packed  so  closely  together  that  the  question 
of  the  presence  or  absence  of  any  substance  between  the 
fibers  and  inclosing  them  could  not  be  answered ;  the  whole 
gave  the  effect  of  aggregate  polarization.  The  above  state- 
ment is  true  for  the  greater  portion  of  each  of  the  slides  — 
the  result  thus  far  was  negative. 

Occasional  irregularities,  however,  in  the  usually  parallel 
fibrous  structure,  which  may  not  inaptly  be  compared  in 
appearance  to  the  grain  of  wood-fiber  in  the  neighborhood 


FOURTH  BRANCHVILLE  PAPER. 


95 


of  a  knot,  as  seen  in  a  smooth  board,  gave  better  results. 
The  fibers  in  such  cases  are  much  curved  and  irregular  in 
outline,  and  so  separated  from  one  another  that  they  are 
seen  to  be  merely  inclosures  in  a  surrounding  matrix.  In 
other  cases,  this  inclosing  material  forms  open  spots,  where 
the  structure  (in  polarized  light)  is  found  to  be  that  of  ordi- 
nary albite,  and  into  this  the  needle-like  fibers  of  the  other 
mineral  project  (this  is  illustrated  in  Figure  15,  a  =  albite). 
Still  again,  on  the  edges  of  the  sections  where  a  degree  of 
thinness  impossible  for  the  whole  slide  is  sometimes  attained, 
a  similar  satisfactory  result  is  reached.  The  fibers  in  such 
cases  are  distinctly  seen,  independently  of  each  other  and  of 
the  inclosing  albite.  They  are  generally  nearly  straight  and 
parallel,  but  not  infrequently  the  shape  is  more  or  less 
irregular;  branching  forms  recalling  some  kind  of  coralline 


FIGURE  15. 


FIGURE  16. 


structure  are  common.  The  latter  forms  are  shown  in  Fig- 
ure 16 ;  the  fibers  here  are  much  more  irregular  and  coarser 
than  is  generally  true.  (Compare  also  Figure  19.)  The 
fibers  are  apparently  rounded,  but  the  outlines  are  usually 
indistinct,  and  the  form  can  be  made  out  only  by  repeatedly 
changing  the  focus  of  the  microscope.  The  explanation  of 
all  these  irregularities  in  outline  is  given  by  the  result  ob- 
tained on  examining  the  sections  cut  transverse  to  the  fibers. 
Several  additional  facts  were  brought  out  in  the  study  of 
the  sections  now  described.  It  was  found  that,  when  exam- 
ined between  crossed  Nicols,  the  extinction  of  the  light  took 
place  parallel  to  the  length  of  the  fibers  ;  moreover,  the  fibers 
have  not  infrequently  a  transverse  fracture,  probably  indi- 


96 


FOURTH  BRANCHVILLE  PAPER. 


eating  cleavage.  The  form  of  the  terminations  of  the  needles 
could  not  be  certainly  observed.  In  cases  like  those  above 
described  (Figure  15),  the  extremities  seem  to  be  given  entire, 
but  no  absolute  assertion  can  be  made  in  regard  to  them. 
In  many  cases,  probably  the  majority,  they  taper  out  gradu- 
ally to  a  fine  point,  while  in  others  they  seem  to  be  terminated 
by  a  low  pyramid. 

The  examination  of  the  other  set  of  sections,  cut  across 
the  fibers,  was  even  more  satisfactory  and  conclusive.  The 
appearance  in  polarized  light,  as  the  plate  is  revolved  on  the 
stage  of  the  microscope,  is  at  once  striking  and  beautiful. 
The  section  as  a  whole  is  divided  into  irregular  patches  (al- 
bite),  changing  from  dark  to  light  and  the  reverse  with  the 
revolution,  giving  the  whole  a  strangely  mottled  look.  Dis- 
tributed closely  and  uniformly  through  this  matrix  are  seen 
also  minute  areas  of  another  substance,  sometimes  curved 
but  generally  bent  at  an  angle  of  60°  or  120°  ;  they  are  un- 
changed by  the  revolution  between  the  crossed  Nicols.  The 
effect  will  be  best  appreciated  from  the  accompanying 


FIGURE  17. 


FIGURE  18. 


sketches  (Figures  17  and  18).  When  a  high  power  is  em- 
ployed (say  600  diam.)  and  the  attention  is  confined  to  a 
small  portion  at  once,  it  is  seen  that  these  narrow  bands, 
which  in  a  cursory  glance  under  a  low  power  seem  to  be 
quite  irregular  in  form,  are,  on  the  contrary,  approximately 
in  parallel  position.  The  solid  portions  are  triangular  or 
hexagonal  in  outline,  and  the  bands  are  bent  at  angles  of  60° 
and  120°,  sometimes  so  as  to  form  complete  rings;  —  they 


FOURTH  BRANCHVILLE  PAPER.  97 

are  all  more  or  less  rounded.  In  short,  the  structure  is  that 
of  the  most  regular  pegmatite  or  "  graphic  granite,"  and  the 
explanation  is  the  same.  These  regular  forms,  like  those 
of  the  quartz  in  the  feldspar  in  the  other  case,  are  due  to 
the  restricted  crystallization  in  the  albite  of  the  new  mineral 
in  question.  They  mark  the  mineral  as  belonging  to  the  hex- 
agonal system,  and  the  result  of  the  optical  examination  both 
parallel  and  transverse  to  the  fibers  confirms  this  conclusion. 

Taking  the  section  as  a  whole,  there  are  portions  in  which 
the  directions  of  the  new  mineral  are  quite  irregular,  but  for 
the  greater  part  there  is  an  obvious  tendency  toward  regu- 
larity, sometimes  leading  to  most  perfect  forms.  As  would 
be  expected,  the  axial  directions  (60° )  change  at  small  dis- 
tances, so  that  a  given  set  of  directions  belongs  only  to  a  lim- 
ited area  ;  this  is  obviously  determined  by  the  inclosing  albite. 

We  are  now  able  to  connect  the  results  of  the  microscopic 
examination  with  those  of  the  earlier  chemical  investigation. 
The  inclosing  material  in  which  the  fibers  lie  is  the  albite ; 
this  is  proved  indeed  by  what  has  been  stated,  and  moreover 
by  the  fact  that  it,  whenever  distinctly  separate,  has  the  same 
structure  as  in  undoubted  cases  of  the  same  pseudomorphous 
material ;  it  is  also  shown  by  the  examination  of  the  insolu- 
ble portion  alluded  to  before,  for  in  this  the  fibers  have  been 
removed  and  the  matrix  left  unattacked.  The  inclosed  min- 
eral is  that  which  with  the  albite  makes  up  the  ft  spodumene, 
having  the  composition  Li2Al2Si2O8. 

In  view  of  the  fact  that  this  lithia-bearing  mineral  is  thor- 
oughly defined,  as  well  crystallographically  as  chemically, 
and  considering,  moreover,  the  important  part  it  plays  in 
the  history  of  the  spodumene,  we  feel  obliged  to  give  it  a 
distinctive  name.  We  call  it  eucryptite^  from  ev  well,  and 
/cpvTrrds  concealed. 

EUCRYPTITE  crystallizes  in  the  hexagonal  system,  with  prob- 
ably basal  cleavage.  Its  specific  gravity,  calculated  from  that 
of  ft  spodumene  2.647,  and  that  of  the  pseudomorphous 
albite  2.637,  is  2.667.  It  gelatinizes  with  hydrochloric  acid  and 
fuses  easily.  It  is  a  unisilicate,  and  its  chemical  composition 


98  FOURTH  BRANCHVILLE  PAPER. 

is  expressed  by  the  formula  Li2Al2Si2O8  =  silica  47.51,  alumina 
40.61,  lithia  11.88  =  100.  Its  mineralogical  relations  are  not 
very  certain;  still,  in  form,  and  essentially  in  composition, 
it  is  analogous  to  nephelite.  It  also  might  be  viewed  as  a 
lithia-anorthite,  it  having  the  same  ratio  as  anorthite,  though 
it  is  different  crystallographically.  On  the  other  hand,  the 
fact  that  it  changes  so  readily  into  muscovite,  and  has  the 
same  ratio  as  the  normal  varieties  of  that  species,  might 
seem  to  place  it  near  it;  but  it  certainly  has  no  micaceous 
structure.  The  true  lithia  mica  (lepidolite)  has  a  very  different 
composition. 

2.    Cymatolite. 

The  name  cymatolite  was  given  in  1867  by  Professor 
Shepard  to  a  mineral  found  at  Goshen  and  Norwich,  Mass.,  a 
result  of  the  decomposition  of  spodumene.  The  analysis  given 
by  him  left  the  composition  of  the  supposed  new  mineral 
in  question,  and  this  doubt  was  not  removed  by  a  subsequent 
analysis  by  Mr.  B.  S.  Burton.  Mr.  Julien  gives  in  his  paper 
several  analyses  of  cymatolite  which  agree  well  together  and 
which,  correspond  to  a  simple  chemical  formula.  In  our 
earlier  investigations  we  assumed  it  to  be  an  established  point 
that  the  species  was  a  good  one  and  had  a  definite  composi- 
tion. This  assumption  was  confirmed  by  two  closely  agreeing 
analyses  (given  below)  made  upon  the  Branchville  material. 
Further  study,  however,  which  was  made  necessary  by  the 
results  reached  in  the  case  of  yS  spodumene  —  for  the  cymatolite 
is  directly  derived  from  the  /5  spodumene  —  has  convinced  us 
that  the  supposed  species  is  only  a  remarkably  uniform  and 
intimate  mechanical  mixture  of  muscovite  and  albite.  We  shall, 
howrever,  throughout  this  paper  retain  the  name  cymatolite  as  a 
convenient  way  of  designating  this  interesting  compound  sub- 
stance, and  shall  describe  it  first  as  if  it  were  a  true  species. 

The  physical  characters  of  the  cymatolite  of  Branchville 
are  as  follows :  it  has  a  distinct  fibrous  structure,  sometimes 
straight  but  more  generally  wavy.  It  is  also  at  times  con- 
fusedly fibrous  and  again  scaly.  The  specific  gravity  =  2.692- 


FOURTH  BRANCHVILLE  PAPER.  99 

2.699.  The  color  is  generally  white,  but  it  is  often  slightly 
discolored,  and  occasionally  it  has  a  faint  pink  hue. 

As  has  been  stated  on  a  previous  page,  the  crystals  of 
spodumene,  which  have  been  altered  to  cymatolite,  are  numer- 
ous and  often  very  large.  The  way  in  which  the  fibrous 
structure  is  developed  is  seen  in  Figure  2,  which  is  a  section 
across  the  prism.  It  is  usually  true,  as  seen  here,  that  the 
direction  of  the  fibers  at  the  edge  is  at  right  angles  to  the 
bounding  surface.  In  the  interior  the  structure  is  more  irreg- 
ular and  the  fibers  interlace  in  an  intricate  manner,  giving 
sometimes  a  feather-like  appearance.  Usually  all  trace  of  the 
original  prismatic  structure  and  cleavage  of  the  spodumene 
has  disappeared.  In  rare  cases,  however,  in  the  interior  of  a 
crystal  this  longitudinal  structure  is  still  apparent,  although 
the  direction  of  the  fibers  remains  transverse.  (Compare  also 
other  figures  in  the  plate,  in  which  c  —  cymatolite.) 

Two  analyses  of  cymatolite  have  been  made  by  Mr.  Penfield. 
No.  1  was  made  from  a  portion  of  an  entirely  altered  crystal ; 
it  was  perfectly  white  and  apparently  free  from  any  impurities. 
The  results  are  as  follows : 

No.  1,  G.  =  2.692.       I.  II.  III.  Mean.  Ratio. 

SiO2  59.38  59.38  0.989        4.00 

A12O3  26.67  26.67  0.259        1.05 

CaO  0.62  0.62      0.011  ^ 

Na.20  ...  7.66        7.70          7.68      0.124 

K20  ...  3.53        3.49          3.51      0.037  f 

H2O  2.01  2.01      0.111  J 

99.87 

The  second  analysis  was  made  on  the  pure  mineral  associated 
on  the  same  crystal,  which  afforded  sample  2  of  /3  spodumene. 
The  results  afforded  are  as  follows : 

No.  2,  G.  =  2.699.        I.  II.  Mean.  Ratio. 

1.009        4.00 
0.256        1.016 


SiO2 

60.61 

60.49 

60.55 

A1203 

26.37 

26.39 

26.38 

MnO 

0.08 

0.06 

0.07 

Na20 

8.08 

8.16 

8.12 

0.13U 

K20 

3.33 

3.35 

3.34 

0.035  1 

Li20 

0.17 

0.17 

0.17 

0.006  [ 

H20 

1.65 

1.66 

1.65 

0.091  J 

0.263        1.044 
u.uuo  i 

0.091  J 

100.29   100.28   100.28 


100  FOURTH  BRANCHVILLE  PAPER. 

The  agreement  between  these  two  analyses  is  as  close  as 
could  be  expected ;  the  ratio  obtained  from  No.  2  is  nearly 

E20  :  A1203 :  Si02  =  1:1:4. 

This  is  the  same  ratio  as  that  obtained  for  spodumene  and  ft 
spodumene.     The  formula  is  therefore 

(Na,  K,  H)2Al2Si4012  -  (K,  H)2Al2Si208  +  Na2Al2Si6016. 

Since  the  cymatolite  is  certainly  derived  from  the  ft  spodu- 
mene, while  the  latter  substance  has  been  proved  to  be  a 
mixture  of  albite  and  what  —  as  was  shown  —  has  the  compo- 
sition of  a  lithia  muscovite,  the  fact  that  the  formula  of 
cymatolite  can  be  written  as  a  compound  of  one  molecule 
muscovite  and  one  molecule  albite  is  significant.  Were  no 
other  facts  at  hand  the  conclusion  that  cymatolite  also  must  be 
a  mechanical  mixture  could  hardly  be  questioned.  The  facts, 
however,  are  in  themselves  sufficient  to  prove  this,  independent 
of  any  other  considerations.  It  may  be  mentioned  that  the 
chemical  method  of  attacking  the  problem,  employed  in 
the  case  of  the  ft  spodumene,  is  not  here  applicable,  since 
the  muscovite  is  not  decomposed  by  hydrochloric  acid.  A 
preliminary  examination  was  made  with  sulphuric  acid,  which 
resulted  in  showing  that  the  cymatolite  was  attacked  by  it, 
as  was  the  mica  of  the  locality,  while  the  albite  was  barely 
so.  This  method  was,  however,  not  carried  further,  for  the 
microscope  gave  all  the  solution  that  could  be  desired. 

A  considerable  number  of  sections  of  cymatolite,  both  in  its 
purest  normal  varieties,  and  in  its  transition  forms  from  ft 
spodumene  on  the  one  hand  and  to  albite  on  the  other,  were 
examined.  The  result  not  only  proved  the  fact  of  the  mixture 
of  muscovite  and  albite,  but  also  gave  the  explanation  for 
the  remarkable  uniformity  of  the  analyses,  for  in  most  cases 
the  mixture  is  in  the  highest  degree  intimate.  A  section  of 
cymatolite  like  that  represented  in  Figure  \c  (Plate),  when 
examined  in  polarized  light,  is  found  to  consist  of  long, 
slender,  somewhat  curved  fibers,  giving  very  brilliant  colors 


FOURTH  BRANCHVILLE  PAPER.  101 

and  showing  the  characteristic  structure  of  mica,  and  between 
them  grayish  portions  of  albite.  In  some  cases  the  fibers  of 
mica  are  so  close  together  that  the  albite  is  invisible,  but  in 
others  they  spread  out  divergent  and  then  the  background 
of  the  other  mineral  is  clearly  seen.  Still  again,  the  mica 
needles  are  few,  and  run  out  in  brilliant  lines  over  a  broad 
surface  of  albite. 

The  sections  increase  in  beauty  with  the  irregularity  of  the 
structure  of  the  cymatolite.  For  example,  two  sections  were 
made  from  the  crystal  represented  in  Figure  2  (Plate).  "  One 
of  these  was,  like  the  figure,  transverse,  and  the  other  was 
vertical,  and  showed  something  of  the  prismatic  structure  of 
the  original  spodumene.  All  the  details  of  the  structure 
came  out  most  clearly  in  the  sections  in  polarized  light.  The 
feather-like  structure  was  particularly  distinct  and  beautiful : 
a  deeply  colored  rib  of  mica,  and  from  this  diverging  regularly 
on  both  sides  the  narrow  fibers  of  the  same  mineral,  the 
albite  between  them  becoming  more  and  more  distinct  as  their 
distance  apart  increased.  Other  sections  were  examined  of 
the  scaly  varieties  of  cymatolite,  where  the  mica  scales  were 
parallel  to  the  surface.  In  these  the  albite  had  the  mottled 
appearance  in  polarized  light,  mentioned  under  ft  spodumene, 
and  the  mica  was  scattered  very  uniformly  as  brilliantly 
colored  scales  through  it.  Other  sections  transverse  to  the 
fibers,  in  the  distinctly  fibrous  kinds,  gave  somewhat  different 
effects.  Many  details  could  be  added,  but  enough  has  been 
said  to  make  the  character  of  the  observations  apparent  on 
which  the  statement  as  to  the  compound  nature  of  cymatolite 
is  based.  The  mica  and  albite  are  always  distinct  from  one 
another.  In  some  cases  they  both  appear  in  larger  masses 
having  segregated  together  in  the  process  of  alteration.  More 
is  said  about  this  later. 

The  only  foreign  mineral  observed  in  the  slides  was  one 
which  occurs  in  hexagonal  prisms,  and  can  hardly  be  anything 
but  apatite,  as  it  agrees  optically  and  crystallographically 
with  that  species.  It  is  seen  scattered  through  the  cymatolite 
sometimes  rather  abundantly,  occasionally  also  in  the  /3  spod- 


102 


FOURTH  BRANCHVILLE  PAPER. 


umene,  it  is,  however,  not  for  a  moment  to  be  confounded  with 
eucryptite.  The  presence  of  apatite  would  explain  the  lime 
found  in  analysis  1  of  cymatolite. 

Certain  of  the  sections  which  show  the  transition  from  (3 
spodumene  to  cymatolite  are  most  interesting  and  instructive. 
While  in  much  of  the  cymatolite  there  seems  to  have  been  a 
tendency  to  the  partial  separation  of  the  mica  and  albite  there 
are  other  specimens  in  which  the  two  are  as  intimately  mixed 
as  the  eucryptite  and  albite  in  the  /3  spodumene.  In  cases 
like  those  last  named,  the  structure  of  the  cymatolite  is 
exactly  that  of  the  ft  spodumene,  only  that  the  rounded  fibers 
of  eucryptite  have  been  replaced  by  the  thin  elongated  scales 
of  mica,  proving  that  the  one  has  been  formed  from  the  other. 
In  still  other  cases  we  may  pass  on  the  same  slide  from 
normal  cymatolite  on  the  one  side  to  normal  /3  spodumene  on 
the  other.  Between  them  is  a  zone  where  the  two  substances 
shade  off  into  one  another,  in  other  words  where  the  change 
of  the  eucryptite  is  only  partial.  This 
will  be  understood  from  Figure  19. 
As  here  seen,  some  of  the  fibers  are 
apparently  unchanged,  while  others  are 
partly  altered,  the  last  containing  many 
minute  scales  of  mica,  often  packed 
closely  together.  These  small  scales 
are  irregularly  situated,  often  across  the 
original  fiber  of  eucryptite :  the  direc- 
tion can  always  be  observed  both  by 

the  cleavage  line  and  too  by  the  direction  of  the  extinction  of 
the  light  between  crossed  Nicols.  Where  the  process  has 
been  completed,  however,  the  scale  of  mica  is  generally  parallel 
to  the  line  of  the  original  eucryptite.  The  eucryptite  fibers 
along  this  intermediate  zone,  even  when  mica  scales  are  not 
visible,  have  generally  lost  their  smoothness  of  outline,  and 
sometimes  have  separated  into  lines  of  minute,  irregular,  trans- 
parent granules. 

The  transition  of   yS  spodumene  into   cymatolite  can   also 
often  be  seen  by  the  unaided  eye,  along  the  line  of  contact. 


FIGURE  19. 


FOURTH  BRANCHVILLE  PAPER.  103 

In  such  cases  the  silvery  lines  of  mica,  though  the  scales  are 
too  minute  to  be  distinguished,  can  be  seen  shooting  up  into 
the  compact  /3  spodumene. 

Greneral  Summary.  —  The  remarks  in  the  preceding  para- 
graphs may  be  summed  up  as  follows :  —  The  spodumene  was 
subjected  to  the  action  of  solutions  containing  respectively 
soda  and  potash.  The  first  action  of  the  soda  solution,  by 
the  partial  exchange  of  alkali,  resulted  in  the  formation,  from 
the  spodumene,  of  an  apparently  homogeneous  but  really 
complex  substance,  consisting  of  equal  parts  molecularly  of 
albite  and  a  new  lithia  silicate  (eucryptite.)  A  further  action 
of  the  soda  solution  (sodium  silicate),  by  the  complete  change 
of  alkali  and  the  accompanying  assumption  of  silica,  led  in 
some  cases  to  the  formation  of  albite.  On  the  other  hand, 
the  action  of  the  potash  more  frequently  changed  the  lithia 
silicate,  above  named,  into  normal  muscovite,  so  that  another 
apparently  homogeneous  but  really  complex  substance  re- 
sulted, cymatolite,  consisting  of  muscovite  and  albite  in  equal 
molecular  proportions;  again,  the  segregation  of  these  two 
minerals  produced,  in  place  of  normal  cymatolite,  a  mixture 
of  separate  masses  of  albite  and  mica.  Still  further  the  action 
of  the  potash,  by  an  exchange  of  alkali  and  simultaneous 
assumption  of  silica,  led  to  the  formation  of  potash-feldspar 
or  microcline.  In  some  cases  the  result  was  a  coarse  mixture 
of  the  mica  and  the  two  feldspars.  Finally,  the  action  of  the 
potash  solution,  and  the  simultaneous  loss  of  silica,  led  to 
the  formation  from  the  original  spodumene  of  a  mineral  very 
closely  related  to  mica,  namely  killinite. 

Two  questions  arise  here,  to  neither  of  which  we  can  give 
a  very  satisfactory  answer.  The  first  is  as  to  the  source  of 
the  soda  and  potash  involved  in  the  changes  that  have  been 
described  —  to  this  nothing  more  can  be  said  than  that  they 
were  probably  furnished  by  the  previous  decomposition  of 
feldspars,  though  under  just  what  conditions  we  are  unable 
to  say. 

The  other  question  is  as  to  the  final  disposition  of  the  lithia 
removed  from  the  spodumene  —  this  seems  to  have  disappeared 


104  FOURTH  BRANCHVILLE  PAPER. 

entirely,  unless  the  fact  that  some  of  the  biotite  in  the  vein 
now  carries  lithia  may  account  for  some  of  it.  In  this  connec- 
tion it  should  be  stated  that  the  manganese  triphylite  — 
lithiophilite  —  is  certainly  an  original  mineral  of  the  vein,  and 
occurs  rather  abundantly  with  the  massive  spodumene.  Its 
decomposition  has  also  led  to  an  increase  of  this  supply  of 
lithia.  Furthermore,  it  is  more  than  possible  that  the  forma- 
tion of  the  remarkable  series  of  phosphates  of  manganese, 
described  by  us  from  this  locality,  was  connected  with  the 
extensive  changes  in  the  spodumene.  The  fact  that  two  of 
the  phosphates  are  almost  unique  among  that  group  of  min- 
erals in  containing  alkalies  (see  analyses  of  dickinsonite  and 
fillowite  in  our  earlier  papers)  would  almost  prove  this.  The 
lithiophilite  may  be  then  the  original  phosphate  of  manganese 
from  which  the  others  have  been  derived.  We  shall  return 
to  this  last  subject  at  some  future  time. 

NOTE.  —  It  has  been  necessary  to  shorten  this  article  by  omit- 
ting several  pages  devoted  to  descriptions  of  pseudomorphs  of 
albite,  muscovite,  microcline,  and  killinite  after  spodumene,  and 
a  general  discussion  of  pseudomorphs  of  vein-granite.  —  EDITOR. 


FIFTH    BRANCHVILLE   PAPER. 

BY  GEORGE  J.  BRUSH  AND  EDWARD  S.   DANA. 

WITH  ANALYSES   OF   SEVEEAL  MANGANESIAN 
PHOSPHATES. 

BY  HORACE  L.   WELLS. 
(From  Am.  Jour.  Sci.,  1890,  vol.  39,  pp.  201-216.) 

IT  is  now  nearly  twelve  years  since  we  published  our  first 
paper  upon  the  Branchville  minerals.  It  will  be  remembered 
that  the  material  which  formed  the  basis  of  our  early  work  was 
that  which  Mr.  Fillow  had  brought  to  light  in  his  excavations, 
some  two  years  previous,  in  search  for  mica.  It  was  this  lot  of 
minerals,  sagaciously  selected  and  preserved  by  Mr.  Fillow, 
that  we  found  so  remarkably  rich  in  phosphates  of  manganese, 
including  a  number  of  new  and  interesting  species.  During 
the  years  of  1878  and  1879,  we  carried  on  a  somewhat  extended 
search  for  these  minerals  in  the  ledge  from  which  they  had 
been  obtained,  but  the  spot  from  which  the  most  interesting 
specimens  had  been  derived  was  very  unfavorably  situated  for 
work,  being  ten  feet  or  more  below  the  level  of  the  ground,  and 
our  efforts  were  only  in  part  successful.  Some  of  the  results 
we  have  already  announced  in  subsequent  papers. 

Perhaps  the  most  important  result  of  our  early  explorations 
was  to  prove  the  presence  of  large  amounts  of  potash  feldspar 
(microcline)  and  quartz  in  the  vein  —  in  fact,  before  we  ceased 
our  private  work,  we  had  brought  to  the  surface  several 
hundred  tons  of  these  minerals.  This  material  was  of  so  excel- 
lent quality  for  technical  use  and  the  supply  seemed  to  be  so 
large  that  negotiations  were  presently  entered  into  between  Mr. 
Fillow,  the  owner  of  the  property,  and  the  Messrs.  Smith, 
of  the  Union  Porcelain  Works,  of  Greenpoint,  New  York, 


106  FIFTH  BRANCHVILLE  PAPER. 

with  the  final  result  of  the  sale  of  the  property  to  the  latter 
gentlemen.  This  was  accomplished  in  1880.  Since  that  time 
the  work  of  quarrying  for  feldspar  and  quartz  has  been  carried 
forward  uninterruptedly  and  with  gratifying  success ;  up  to 
the  present  time  Mr.  Fillow  informs  us  that  from  three  to 
four  thousand  tons  of  feldspar  and  four  thousand  tons  of 
quartz  have  been  shipped  from  the  locality.  The  arrangement 
has  proved  also  a  very  successful  one  from  a  scientific  point 
of  view.  The  Messrs.  Smith  have  very  liberally  placed  at  our 
disposal  all  the  material  obtained  from  the  locality  which  was 
of  no  technical  value,  while  the  daily  presence  of  Mr.  Fillow, 
with  his  active  interest  and  keen  eye,  has  resulted  in  saving 
for  science  practically  everything  which  the  locality  has 
yielded.  The  covering  of  earth  was  early  removed,  and  the 
ledge  opened  to  as  great  a  depth  as  the  drainage  would  allow ; 
since  then  the  drain  has  been  repeatedly  cut  deeper  until  in 
the  summer  of  1888,  ten  years  after  our  first  work,  the  time 
to  which  we  had  been  constantly  looking  forward  arrived  and 
the  deep  spot  from  which  the  first  supply  of  phosphates  came 
was  reached. 

In  the  mean  time,  however,  the  work  had  not  been 
unproductive,  and  the  contents  of  our  third  paper  upon 
certain  deposits  of  lithiophilite,  eosphorite  and  other  associated 
minerals,  and  of  our  fourth  paper  upon  the  spodumene  and  its 
alteration-products,  show  in  part  what  was  accomplished.  In 
addition  to  what  is  mentioned  in  these  papers,  the  locality  has 
at  several  different  times  yielded  a  not  inconsiderable  amount 
of  uraninite,  in  part  in  octahedral  crystals  with  a  specific 
gravity  of  9.3 ;  this  has  been  investigated  chemically  by 
Comstock.*  With  the  uraninite  have  been  found  two  or 
more  uranium  phosphates  which  have  not  as  yet  been 
thoroughly  studied.  Columbite  has  also  been  found  in 
considerable  quantity,  aggregating  more  than  500  pounds. 
This  occurs  in  crystalline  masses,  and  in  part  well  developed 
crystals  and  groups  of  crystals  in  parallel  position  of  remarkable 
size.  It  has  a  specific  gravity  of  5.78,  and  as  shown  by  an 

*  Am.  Jour.  Sci.,  1880,  vol.  19,  p.  220. 


FIFTH  BRANCHVILLE  PAPER.  107 

analysis  by  T.  B.  Osborne  *  contains  19.2  per  cent  of  Ta2O6. 
Another  kind  of  columbite  has  also  been  found  in  minute 
reddish  brown  translucent  crystals  usually  implanted  upon  the 
spodumene.f  This  variety  Comstock  has  shown  to  be  excep- 
tionally interesting  in  the  fact  that  it  contains  manganese  with 
practically  no  iron,  and  further  has  the  niobium  and  tantalum 
in  the  ratio  of  1:1;  it  has  a  specific  gravity  of  6.59.  Other 
points  of  interest  that  have  been  brought  out  are  the  occurrence 
on  a  rather  abundant  scale  of  a  mineral,  both  massive  and 
indistinctly  fully  crystallized,  which  resembles  cyrtolite  but 
has  not  yet  been  investigated ;  also  of  smoky  quartz,  in  part 
well  crystallized,  and  remarkable  for  its  richness  in  fluid 
inclusions  (CO2,  etc.)  as  described  microscopically  and  chemi- 
cally by  Hawes  and  Wright ;  {  also  of  beryl  in  large  columnar 
masses  sometimes  two  feet  or  more  in  length ;  still  further  of 
albite  in  finely  crystallized  specimens.  Apatite  has  been 
found  in  a  variety  of  forms;  one  variety,  of  a  dark  bluish 
green,  has  been  found  by  Penfield  §  to  contain  10.6  per  cent  of 
MnO.  Other  kinds  are  interesting  crystallographically  and 
resemble  the  Swiss  crystals  in  habit  and  complexity.  Mica 
has  been  obtained  in  limited  amount  of  a  merchantable  form 
(300  pounds  of  plates  cut  to  pattern)  ;  the  most  common 
variety,  however,  is  that  occurring  in  curved  plates,  presenting 
a  smooth  convex  surface  like  a  watch-glass ;  these  aggregates 
have  a  radiated  as  well  as  concentric  structure.  Specimens  of 
the  Branchville  mica  have  been  analyzed  by  Rammelsberg.|| 

The  most  important  developments,  however,  have  been  those 
of  the  summers  of  1888  and  1889,  when  considerable  quantities 
of  the  manganesian  phosphates  were  brought  to  light.  This 
result  has  been  especially  gratifying  to  us,  since  it  has  given  us 
specimens  of  all  but  one  of  the  new  species  described  in  1878, 
several  of  which  we  had  almost  despaired  of  finding  again. 
It  has  also  afforded  another  new  member  of  the  triphylite 
group,  a  sodium-manganese  phosphate,  which  we  shall  call 
natrophilite.  Besides  this  we  have  identified  another  phosphate 

*  Am.  Jour.  Sci.,  1885,  vol.  30,  p.  336.          t  Ibid.,  1880,  vol.  19,  p.  131. 
J  Ibid.,  1881,  vol.  21,  pp.  203,  209.  §  Ibid.,  1880,  vol.  19,  p.  367. 

||  Jahrb.  Min.,  ii,  224,  1885. 


108  FIFTH  BRANCHVILLE  PAPER. 

of  manganese,  and  one  which  from  the  first  we  had  hoped  to 
find,  viz. :  the  rare  mineral  hureaulite,  thus  far  only  certainly 
known  from  Limoges,  commune  of  Hureaux,  in  France. 

The  general  method  of  occurrence  of  the  phosphates  of 
manganese  is  such  as  to  confirm  the  opinion  that  we  have 
expressed  in  a  former  paper,  that  the  manganesian  triphylite 
or  lithiophili te  is  the  parent  species.  This  is  beyond  all  doubt 
an  original  mineral  in  the  vein,  occurring  intimately  associated 
with  the  albite,  quartz,  and  spodumene.  With  it,  sometimes 
entirely  inclosed  by  it,  we  find  another  of  the  Branchville 
species,  triploidite,  which  seems  to  be  also  an  original  mineral. 

NATEOPHILITE. 

The  sodium-manganese  member  of  the  triphylite  group,  to 
which  we  give  the  name  natrophilite,  has  been  identified  only 
in  the  material  obtained  during  the  last  summer.  It  occurs 
sparingly,  usually  closely  associated  with  lithiophilite,  and 
upon  a  superficial  examination  could  be  confounded  with  it, 
although  distinguishing  characters  are  not  wanting.  It  ap- 
pears in  cleavable  masses  for  the  most  part,  the  cleavage 
surfaces  often  broad  and  showing  something  of  a  pearly 
luster.  Occasionally  smaller  grains  appear  imbedded  in  the 
cleavage  mass,  and  these  show  at  times  a  more  or  less  distinct 
crystalline  form.  On  one  of  these  the  usual  planes  of  tri- 
phylite were  identified,  110,  120,  021,  001  (cleavage).  The 
angles  could  not  be  obtained  accurately  but  were  sufficient 
to  determine  the  forms,  viz. : 

Natrophilite.  Triphylite. 

110  A  1TO  =  50°  30'  47° 


120  A  150=  87°  82°  V 

001  A  032  =  47°  -  49°  46°  29' 

In  crystalline  form,  then,  it  agrees,  as  was  to  be  expected,  with 
triphylite  and  lithiophilite.  Optically  it  also  corresponds  so 
far  as  it  has  been  investigated  ;  the  optic  axes  lie  in  the  basal 
section  and  the  acute  bisectrix  (positive)  is  normal  to  the 
brachypinacoid.  The  characteristic  basal  cleavage  is  always  a 
prominent  character,  but  the  brachydiagonal  cleavage  010  is 


FIFTH  BRANCHVILLE  PAPER.  109 

less  distinct  than  is  shown  by  lithiophilite,  and  the  prismatic 
cleavage  (110)  is  interrupted;  the  measured  angle  was  50°  ; 
these  cleavages  are  seen  more  clearly  in  thin  sections.  The 
fracture  is  conchoidal,  more  perfectly  so  than  with  lithiophilite. 
The  color  is  a  rather  deep  wine-yellow,  much  like  that  of  the 
Brazilian  topaz.  The  luster  is  brilliant  resinous  to  nearly 
adamantine ;  it  was,  in  fact,  the  brilliancy  of  the  luster  which 
first  attracted  our  attention,  and  which  is,  so  far  as  the  eye  is 
concerned,  its  most  distinguishing  character.  The  mineral 
itself  is  perfectly  clear  and  transparent,  but  the  masses  are 
much  fractured  and  rifted.  The  surfaces  are  often  covered  by 
a  very  thin  scale  of  an  undetermined  mineral,  having  a  fine 
fibrous  form,  a  delicate  yellowish  color,  and  silky  1  aster.  This 
same  mineral  penetrates  the  masses  wherever  there  is  a  frac- 
ture surface  of  cleavage  or  otherwise.  What  the  exact 
nature  of  this  mineral  is  we  are  unable  to  say,  since  the 
amount  is  too  small  to  admit  of  a  satisfactory  determination. 
It  appears  to  be  a  manganesian  phosphate.  It  is  evidently  an 
alteration-product  and  would  seem  to  imply  that  natrophilite 
is  rather  subject  to  easy  chemical  change.  In  any  case,  this 
silky  film  is  one  of  the  characteristic  features  of  the  mineral, 
and  directs  attention  to  it  at  once  even  over  the  surface  of  a 
hand  specimen  where  it  is  associated  with  lithiophilite  and 
perhaps  three  or  four  other  of  these  phosphates. 

Before  the  blowpipe  natrophilite  fuses  very  easily  and 
colors  the  flame  intensely  yellow,  thus  being  at  once  distin- 
guished from  lithiophilite.  It  also  gives  the  usual  reactions 
for  manganese.  The  following  is  an  analysis  of  natrophilite 
made  by  Wells.  The  specific  gravity  on  two  fragments  was 
found  to  be  3.40  and  3.42. 

Ratio. 

0.289  =  1.00  =  1 


I. 

n. 

in. 

Mean. 

P  O 

41.03 

41.03 

MnO 

38.19 

38.19 

FeO 

3.06 

3.06 

Na2O 

16.77 

16.81 

16.79 

Li2O 

0.20 

0.19 

0.19 

H2O 

0.40 

0.45 

0.43 

Insol. 

0.81 

0.81 

0.81 

0.81 

100.50 

110  FIFTH  BRANCHVILLE  PAPER. 

The  formula  is  therefore  R2O  .  2RO  .  P2O5  or  RRPO4,  or 
essentially  NaMnPO4.  It  will  be  noticed  that  iron  is  present 
in  very  small  amount  only  (3  per  cent)  and  of  lithia  there  is 
hardly  more  than  a  trace  (0.2  per  cent).  With  the  discovery 
of  natrophilite,  the  triphylite  group  receives  an  important 
addition,  and  we  now  have: 

Triphylite,  LiFeP04  )  Connected  by  many  intermediate 

Lithiophilite,  LiMnP04     j"       compounds,  Li(Fe,Mn)P04. 
Natrophilite,  NaMnP04. 

These  three  species  are,  as  is  to  be  expected,  closely  isomor- 
phous.  To  them  is  also  related  in  composition  and  in  some 
degree  in  form  the  new  sodium-beryllium  phosphate,  beryl- 
lonite,  NaBePO4,  which  was  described  by  one  of  us  a  year  and 
a  half  ago.* 

The  relation  of  natrophilite  in  origin  to  the  common  lithio- 
philite  is  an  interesting  question.  In  view  of  the  extensive 
changes  that,  as  we  have  shown,  have  taken  place  in  the  spo- 
dumene,  by  which  the  lithium  has  been  removed  and  its  place 
taken  more  or  less  fully  by  sodium,  or  sodium  and  potassium, 
it  is  natural  to  suggest  that  a  similar  change  has  resulted  in 
forming  the  NaMnPO4  out  of  LiMnPO4,  and  this  we  regard  as 
very  probable.  Its  limited  method  of  occurrence  suggests  the 
same  thing,  although  it  must  be  remarked  at  the  same  time 
that  it  seems  to  pass  into  hureaulite  as  readily  as  the  lithio- 
philite.  If  in  fact  formed  from  lithiophilite,  the  change 
probably  took  place  before  the  formation  of  most  of  the  other 
phosphates. 

HUREAULITE. 

Perhaps  the  most  interesting  of  recent  developments  at 
Branchville  is  the  discovery  of  the  rare  mineral  hureaulite. 
Thus  far  our  knowledge  of  hureaulite  has  been  limited  to  the 
account  of  crystals  from  Limoges  by  Dufre*noyf  and  the  later 
and  more  thorough  description  by  Damour  and  DesCloizeaux.J 

*  Amer.  Jour.  Sci.,  1888,  vol.  36,  p.  290;  1889,  vol.  37,  p.  23. 

t  Ann.  Chim.  Phys.,  xli,  338,  1829.  \  Ibid,  III,  liii,  293,  1858. 


FIFTH  BRANCHVILLE  PAPER.  Ill 

In  addition  we  have  only  the  single  remark  by  Websky  that 
it  probably  occurs  at  Michelsdorf,  Silesia,  with  sarcopside. 

The  crystals  described  by  DesCloizeaux  belong  to  three 
varieties  showing  two  distinct  types  of  form,  though  having 
the  same  composition,  as  shown  by  Damour.  These  varieties 
are  respectively  violet-rose,  brownish  orange,  and  pale  rose- 
pink  in  color.  Their  crystallographic  relation  to  each  other  is 
anomalous,  —  in  fact,  it  would  be  difficult  to  find  another  case 
equally  so.  The  crystals  of  the  two  types  have  the  funda- 
mental prism  in  common,  but  otherwise  no  plane  of  the  one 
occurs  on  the  other,  and  what  is  more  remarkable,  the  symbols 
assigned  to  a  number  of  the  planes  of  the  second  type  are 
complex  in  the  extreme.  The  axial  ratio  calculated  from 
DesCloizeaux's  fundamental  measurements  is 

a  :  b  :  c  =  1.6977  :  1  :  0.8887  ;  ft  =  89°  27'. 

The  planes   observed  on  crystals  of   the   two  types  are  as 
follows : 


The  Branchville  crystals,  like  those  from  Limoges,  vary  in 
color  from  pale  violet  to  reddish  brown  and  deep  orange-red. 
The  habit  of  the  crystals,  however,  is  nearly  constant  and 
the  angles  also,  so  far  as  our  measurements  have  gone ;  they 
correspond  to  the  second  type  of  the  Limoges  crystals.  The 
crystals  are  not  easy  to  decipher,  since  they  are  very  small, 
united  by  parallel  grouping  and  as  a  rule  present  only  a  few 
planes  in  such  a  way  as  not  to  exhibit  the  symmetry.  The 
angles  are  not  as  accurate  as  could  be  desired,  although  the 
crystals  are  much  better  than  those  of  Limoges,  since  Des- 


DesCl. 

i             100 

A1 

n            110 

771 

>              105 

O6 

i             1-5.0.8 

«A 

1              435 

8 

5             TSF  .  5  .  8 

A; 

9             TT.9.10 

X 

3.  11  .  10 

€ 

112  FIFTH  BRANCHVILLE  PAPER. 

Cloizeaux  gives  his  observed  angles  to  whole  degrees  in  many 
cases  and  the  majority  are  stated  to  be  approximations  only. 

For  the  sake  of  greater  simplicity  of  symbols,  the  position 
of  DesCloizeaux  is  modified  somewhat  in  that  his  plane  105 
(o5)  is  taken  as  the  base  and  the  pyramid  8  is  made  the  unit 
pyramid. 

For  fundamental  angles  the  following  have  been  assumed : 

100  A  001  =  84°  1' 
100  A  110  =  62°  21' 
T10  A  101  =  70°  54' 

whence  we  obtain : 

a  :  b  :  c  =  1.9192  :  1  :  0.5242 ;  ft  =  84°  i'. 

The  observed  planes  with  the  symbols  of  the  corresponding 
planes,  so  far  as  observed  by  DesCloizeaux,  are  as  follows  : 

DesCloizeaux. 

a  100  100  hl 

c  .001  105  o5 

m  110  110  m 

a  501  T5 . 0 . 8  aft 

ft  oOl 

p  223 

8  111  435  8 

e  221  5.11.10  e 

k  311  T3.5.8  k 

z  S21 

I  541 

The  attempt  to  transform  the  symbols  of  DesCloizeaux, 
according  to  the  usual  methods,  into  those  required  by  this 
change  of  position  meets  with  only  partial  success.  Thus  the 
plane  19.5.8  becomes  by  the  transformation  111  while  the 
observed  angles  of  DesCloizeaux  make  it  for  the  axial  ratio 
here  taken  511.  As  will  be  seen  below,  the  angles  of  a  num- 
ber of  forms  on  the  Branchville  hureaulite  agree  pretty  well 
with  the  angles  measured  by  DesCloizeaux,  with  the  single 
exception  of  the  prism.  For  this  he  found  119°,  while  we 


FIFTH  BRANCHVILLE  PAPER. 


113 


make  it  for  the  Branchville  crystals  124°  42'.  It  is  this 
discrepancy  which  causes  the  want  of  agreement  which  we 
have  just  alluded  to.  Furthermore,  it  is  seen  that  the  complex 
symbols  of  several  of  the  planes,  in  DesCloizeaux's  position 
and  referred  to  his  axes,  become  simplified  when  referred  to 
the  axes  here  adopted.  Of  the  planes  noted  by  DesCloizeaux 
on  type  2,  all  but  one  (11.9.10),  it  will  be  seen,  occur  on  the 
Branchville  crystals  and  to  this  the  symbol  532  probably 
belongs  in  our  position.  Of  the  forms  of  the  first  type  only 
the  prism  occurs  with  us,  but  to  the  other  planes  the  probable 
symbols  in  our  position  may  be  assigned. 


DesCloizeaux. 

001 
Oil 


DesCloizeaux. 

103  311  u  T2.3.2? 

T53  341  t  561  ? 


The  table  of  angles,  here  omitted,  gives  the  more  impor- 
tant angles  calculated  from  our  axial  ratio  compared  with 
our  measurements  and  also  with  the  measured  angles  of 
DesCloizeaux.  Although  the  correspondence  between  our 
measured  and  calculated  angles  is  not  in  all  cases  as  great  as 
could  be  desired,  the  agreement  is  as  close  as  could  perhaps 
be  expected  from  the  nature  of  the  material.  It  has  been 
stated  that  the  crystals  are  often  grouped  in  parallel  position, 
but  as  is  common  in  such  cases,  the  parallelism  is  not  perfect 
and  furthermore  the  parts  show  slight  variations  in  position, 
even  when  the  planes  are  smooth,  which  are  doubtless  to  be 
referred-  to  the  same  cause. 


FlGUKE   1. 


114 


FIFTH  BRANCHVILLE  PAPER. 


The  habit  of  the  Branchville  crystals  is  short  prismatic,  as 
shown  on  Figure  1 ;  a  basal  projection  of  a  more  complex 
form  is  given  in  Figure  2.  The  grouping  in  parallel  position 
gives  rise  to  a  repetition  of  the  prismatic  planes  which  may 
result  in  a  deep  striation  or  furrowing  of  this  form.  Besides 
this,  the  zone  of  planes  TTZ,  Z,  &,  a,  is  often  striated  or  channelled 
parallel  to  their  common  direction  of  intersection.  The  crys- 
tals show  rather  perfect  cleavage  parallel  to  the  orthopinacoid. 
For  analysis,  carefully  selected  portions  of  the  purest  crystals 
were  taken  by  Prof.  Wells.  The  specific  gravity  was  found 
to  be  3.149.  The  results  are  satisfactory  as  agreeing  fully 
with  those  of  Damour  and  leading  to  the  same  formula.  For 
comparison  we  quote  Damour's  analysis  of  the  pale  rose 
crystals,  which  differs  but  little  from  that  of  the  yellow 
crystals;  it  is  to  be  noted  that  the  violet  crystals  (type  I) 
have  not  been  analyzed  and  it  is  possible  that  some  difference 
in  composition  may  explain  the  difference  noted  in  the  form. 
The  Branchville  mineral  contains  a  little  less  iron  than  the 
Limoges. 

Limoges. 
G.  =  3.185. 

37.83 
8.73 
41.80 

11.60 

Gangue    0.30 
100.11  100.26 

The  formula  is  5RO  .  2P2O5 .  5H2O  or  H2R5(PO4)4+4H2O. 
The  percentage  composition  calculated  for  manganese  only  is : 
P2O5  38.96,  MnO  48.69,  H2O  12.35  =  100. 

REDDINGITE. 

The  species  reddingite  has  been  known  thus  far  only  in  a 
few  specimens,  showing  it  in  a  granular  form  of  a  reddish 
color,  or  rarely  in  octahedral  crystals  often  superficially  black 
from  oxidation.  The  material  first  found,  though  scanty, 
was  sufficient  to  admit  of  the  determination  of  the  form,  which 
was  shown  to  be  similar  to  that  of  scorodite  and  strengite. 


I. 

Branchville. 
G.  =  3.149. 
II. 

Mean. 

Ratio. 

P0O6 

38.28 

38.44 

38.36 

0.270 

=  1.00 

=  2 

FeO 

4.76 

4.37 

4.56 

0.063  • 

1 

MnO 

42.29 

.  .  . 

42.29 

0.596  ] 

>  0.676 

=  2.50 

=  5 

CaO 

0.94 

.  •  • 

0.94 

0.17    . 

1 

H2O 
Quartz 

12.25 
1.76 

12.15 

12.20 
1.76 

0.678 

=  2.51 

=  5 
( 

OF  THE 

UNIVERSITY 


FIFTH  BRANCHVILLE  PAPER.  115 

Among  the  specimens  recently  discovered  reddingite  is  not 
uncommon,  and  we  have  been  gratified  to  obtain  it  not  only 
well  crystallized  but  also  in  massive  form,  perfectly  fresh  and 
unaltered.  The  color  is  a  pale  rose-pink,  often  hardly  more 
than  a  pinkish-white.  The  most  intimately  associated  min- 
erals are  fairfieldite  and  dickinsonite,  the  latter  of  which  is 
often  imbedded  in  it  in  isolated  scales,  or  more  often  in  stellate 
groups  of  green  folise.  The  octahedral  habit  of  the  crystals, 
which  appear  in  occasional  cavities,  is  usually  apparent  at  a 
glance,  but  not  infrequently  the  crystals  are  distorted  by  the 
elongation  of  a  pair  of  pyramidal  planes,  which  gives  them  a 
misleading  oblique  prismatic  appear- 
ance. The  common  form  of  the  crys- 
tals is  shown  in  Figure  6  of  our  former 
paper,  page  69.  Some  of  the  crystals 
are  more  complex,  Figure  3,  and  show 
also  the  pryamids  r,  s,  and  £,  whose 
symbols  are  respectively  338,  223,  774. 
These  planes  do  not  give  sharp  meas-  FIGURE  3 

urements,  but  the  angles  are  sufficient 
for  identification. 

It  seemed  especially  desirable  to  have  a  new  analysis  of  this 
species,  both  because  the  material  was  more  abundant  and 
better  than  what  we  had  had  before,  and  also  since  the  compo- 
sition —  though  in  fact  fully  established  —  may  have  appeared 
to  some  anomalous,  hi  view  of  its  failure  to  correspond  with 
that  of  scorodite  and  strengite  in  the  degree  of  oxidation  of 
the  manganese  and  in  the  amount  of  water.  The  new  analysis 
by  Wells  fully  confirms  the  former  one  made  by  him,  only 
differing  in  the  larger  percentage  of  ferrous  iron  present.  This 
analysis  of  a  carefully  selected  portion  with  a  specific  gravity 
of  3.204  gave  : 

I.  II.                                           Ratio. 

P2O5          34.90  .  .  .                         0.246  =  1.00  =  1 

FeO            17.13  .  .  .            0.238 ) 

MnO          34.51  .  .  .            0.486  >  0.735  =  2.99  =  3 

CaO             0.63  .  .  .             0.011 > 

H20           13.18  13.18                        0.732  =  2.98  =  3 
Quartz         0.13 
100.48 


116  FIFTH  BRANCHVILLE  PAPER. 

The  formula  is  hence  R3(PO4)2  +  3H2O,  and  if  R  =  Fe  : 
Mn  =  1  :  2,  this  requires  P2O6  34.64,  FeO  17.56,  MnO  34.63, 
H2O  13.17  =  100. 

FAIRFIELDITE. 

Fairfieldite  appears  among  the  specimens  recently  obtained 
not  infrequently,  and  in  a  form  much  fresher  and  purer  than 
that  in  which  we  had  it  before.  It  is  usually  in  foliated 
masses  intimately  associated  with  reddingite  and  hardly  less 
so  with  hureaulite.  The  color  varies  from  white  to  yellowish 
or  greenish  white ;  it  is  usually  perfectly  transparent  and  the 
luster  is  very  brilliant,  varying  from  adamantine  to  pearly, 
according  to  the  surface  on  which  it  is  viewed,  the  latter  on 
the  surface  of  perfect  cleavage.  A  tendency  to  crystallization 
is  at  times  apparent,  but  no  crystals  suitable  for  measurement 
have  been  found,  which  is  to  be  regretted  since  the  early  results 
left  much  to  be  desired.  An  analysis  of  the  perfectly  fresh 
mineral  has  been  made  by  Wells.  This  agrees  with  those  of 
Penfield  previously  published ;  the  amount  of  iron  is  less  and 
that  of  the  manganese  greater,  but  it  is  worthy  of  note  that 
the  ratio  of  2  :  1  for  Ca  :  Mn  -f  Fe  is  still  maintained.*  The 
analysis  of  pure  material  having  a  specific  gravity  of  3.07  is  as 
follows : 

Ratio. 

P2O6  [37.69t]  0.265  =  1.00  =  1 

FeO  3.42  0.047 


MnO  17.40  0.245  J  0-292  =  1.10  =  1 

CaO  30.02  0.536  =  2.02  =  2 

H2O  9.81  0.545  =  2.06  =  2 

Quartz  1.66 

100.00 

The  formula  is  hence  essentially  Ca2Mn(PO4)2  4-  2H2O,  which 
requires  P2O5  39.34,  MnO  19.67,  CaO  31.02,  H2O  9.97  =  100. 
This  analysis  confirms  the  earlier  one  by  Penfield  and  further 

*  It  is  interesting  to  call  attention  here  to  the  identification  of  fairfieldite 
by  Sandberger  at  Rabenstein,  Jahrb.  Min.,  i,  185,  1885.  It  is  also  worthy  of 
note  that  a  new  hydrous  phosphate  of  ferrous  iron  and  calcium,  near  fairfieldite 
but  with  2|H2O,  has  been  recently  named  messelite  by  Muthmann  (Zs.  Kryst, 
xvii,  93,  1889) ;  like  fairfieldite  it  is  triclinic.  Furthermore,  the  brandtite  of 
Nordenskiold  is  Ca2Mn(As04)2  +  2H20,  corresponding  exactly  to  fairfieldite, 
CEfv.  Ak.  Stockh.,  489,  1888,  Groth,  Tab.  Ueb.  Min.,  p.  80, 

t  By  difference. 


FIFTH  BRANCHVILLE  PAPER.  117 

makes  it  probable  that  there  is  a  definite  ratio  of  1  :  2  for 
Mn  (with  Fe)  :  Ca. 

DlCKINSONITE. 

One  of  the  most  remarkable  and  novel  of  the  species  first 
described  from  Branchville  was  the  chlorite-like  dickinsonite ; 
a  mineral  of  a  bright  green  color,  micaceous  structure 
and  pseudo-rhombohedral  form.  Recent  developments  have 
enabled  us  to  add  materially  to  our  knowledge  of  the  species. 
The  number  of  specimens  obtained  is  relatively  large,  and  in 
some  of  them  it  shows  itself  in  tolerably  well-defined  crystal- 
lized forms.  It  will  be  remembered  that  for  our  earlier  work 
we  had  only  one  or  two  minute  crystals.  The  habit  of  most 
of  the  crystals  now  found  differs  from  that  before  described. 
The  hexagonal  form  is  rather  rare  and  the 
crystals  appear  as  rectangular  tables  united 
in  slightly  diverging  groups,  Figure  4. 
A  closer  examination  shows  that  they 
agree  with  the  same  fundamental  form  be- 
fore accepted.  These  crystals  are  elon- 
gated parallel  to  the  orthodiagonal  axis, 
and  the  basal  surfaces  are  bent  and  striated 
in  this  direction.  In  addition  they  show  FIGURE  4. 

on  the  edges,  sometimes  in  traces  only,  the 
pyramidal  planes,  which  when  developed  give  the  hexagonal 
habit  before  noted.  In  addition  to  the  planes  a,  b,  c,  x  (301), 
p  (111)  and  s  (221),  we  have  identified  also  a  steep  clinodome, 
n,  which  has  the  symbol  (051)  and  a  hemi-orthodome,  7 
(103). 

Optically  we  find  the  crystals,  as  before  stated,  to  be  biaxial, 
the  optic  axes  being  situated  in  the  clinodiagonal  section  and 
the  bisectrix  nearly  normal  to  the  cleavage  face ;  the  double 
refraction  is  negative  and  the  axial  angle  large. 

Besides  the  crystals  occasionally  appearing  in  the  cavities, 
and  often  united  in  slightly  diverging  groups  with  edges  par- 
allel to  b  projecting,  the  mineral  occurs  foliated  to  almost 
massive  and  granular,  the  folia,  however,  usually  distinct  and 
often  grouped  in  rosettes  or  stellate  forms. 


118 


FIFTH  BRANCHVILLE  PAPER. 


Dickinsonite  is  the  species  about  whose  composition  we 
felt  most  doubt  when  we  first  published.  The  material  then 
in  hand  was  very  scanty  and  not  entirely  pure,  and  although 
excellent  analyses  were  made  by  Penfield,  their  interpretation 
was  a  matter  of  some  doubt  because  of  admixture  of  more  or 
less  eosphorite  as  well  as  quartz.  Two  independent  sets  of 
new  analyses  have  been  made  by  Professor  Wells.  The 
material  for  the  first  was  picked  with  great  care,  but  in  order 
to  remove  all  question  as  to  whether  the  results  gave  the  true 
composition  of  the  mineral,  a  second  and  independent  analysis 
was  made.  For  this  the  very  best  material  was  selected  and 
after  being  separated  was  minutely  examined  microscopically 
to  make  sure  of  its  purity.  The  results,  as  will  be  seen,  are 
identical  with  those  of  the  first. 

DICKINSONITE,  BRANCHVILLE. 

Analysis  of  first  sample. 
Sp.  gr.  3.143. 


I. 

II. 

Mean. 

Ratio. 

PA 

39.57 

39.57 

0.279  =  1.00  =  1 

FeO 

.  .  . 

13.25 

13.25 

0.184  i 

MnO 

31.74 

231.4 

31.58 

0.445 

CaO 

215 

2.15 

0.039 

MgO 

trace 

0.814  =  2.92  =  3 

Na2O 

7.47 

7.44 

7.46 

0.124 

K20 

1.49 

1.55 

1.52 

0.017 

Li20 

0.20 

0.14 

0.17 

0.005 

H2O 

1.66 

1.65 

1.65 

0.094  =  0.34  =  \ 

Quartz 

2.58 

2.58 

2.58 

99.93 

Analysis 

of  second  sample. 

I. 

II. 

Mean. 

Ratio. 

PA 

40.89 

.  .  . 

40.89 

0.288  =  1.00  =  1 

FeO 

12.96 

.  .  . 

12.96 

0.180  i 

MnO 

31.83 

.  .  . 

31.83 

0.448 

CaO 

2.09 

2.09 

0.038 

MgO 

none 

.  .  . 

0.811  =  2.82  =  3 

Na2O 

.  .  . 

7.37 

7.37 

0.120 

K20 

.  .  . 

1.80 

1.80 

0.019 

Li20 

.  .  . 

0.22 

0.22 

0.006 

H20 

1.64 

1.62 

1.63 

0.092  =  0.32  =  $ 

Quartz 

0.85 

0.79 

0.82 

99.61 

FIFTH  BRANCHVILLE  PAPER.  119 

The  two  samples  were  picked  from  separate  specimens  and 
the  material  was  apparently  very  pure.  Unusual  care  was 
taken  in  picking  the  second  sample,  and  its  purity  is  indicated 
by  the  small  amount  of  quartz  present. 

The  formula  indicated  by  both  the  analyses  is  3RO  .  P2O5, 
JH2O  or  R3(PO4)2  +  JH2O  where  R  =  Mn,  Fe,  Ca,  Na2,  K2 
and  Li2.  There  is  no  simple  ratio  between  the  alkalies  and 
the  remaining  bases.  The  results  vary  considerably  from  those 
of  Penfield  in  his  original  analysis.  This  is  undoubtedly  due 
to  the  fact  that  the  present  material  was  much  purer  than 
that  analyzed  by  him.  Penfield  found  about  14  per  cent  CaO, 
(probably  due  to  admixed  fairfieldite)  only  about  6  per  cent  of 
alkalies  and  3.87  per  cent  of  H2O.  The  formula  which  he 
arrived  at,  however,  is  confirmed  except  in  the  amount  of 
H2O.  It  will  be  seen  that  the  composition  now  established  is 
essentially  the  same  with  that  deduced  for  fillowite  on  the 
basis  of  Penfield's  original  analysis. 

FILLOWITE. 

The  fact  just  stated,  that  our  former  formula  for  fillowite  is 
the  same  as  that  now  obtained  for  dickinsonite,  has  made  us 
very  anxious  to  prove  that  our  early  results  were  trustworthy, 
especially  since  the  material  in  hand  at  the  time  of  our  first 
investigation  was  very  scanty.  Unfortunately,  among  the 
large  number  of  specimens  recently  obtained  from  Branchville, 
we  have  not  succeeded  in  finding  a  trace  of  this  mineral.  We 
have  been  forced  consequently  to  revert  to  the  few  original 
specimens  still  in  hand.  The  best  of  these  we  gave  to  Mr. 
Wells,  and  from  it  he  picked  out  about  0.75  gram,  in  the 
homogeneity  of  which  he  had  entire  confidence.  A  new 
analysis  of  this  has  been  made  by  him  with  the  following 
results ;  for  comparison  we  quote  the  original  analysis  by 
Penfield. 


P206 

39.68 

0.279 

Feo 

9.69 

0.135  , 

1 

MnO 

39.58 

0.557 

CaO 

3.63 

0.065  ! 

\  0.847 

Na20 

5.44 

0.088 

Li20 

0.07 

0.002  J 

1 

H20 

1.58 

0.088 

Quartz 

1.02 

120  FIFTH  BRANCHVILLE  PAPER. 

Ratio.  Analysis  (1878)  Penfield. 

1.00        39.10 
9.33 
39.42 

3.04  4.08 
5.74 
0.06 

0.31          1.66 
0.88 
100.69  100.27 

It  will  be  seen  that  the  two  analyses  agree  throughout  and 
the  formula  is  the  same,  viz. :  R8P2O8  -f  JH2O.  As  noted 
above,  it  is  identical  with  that  of  dickinsonite,  although 
the  latter  species  contains  more  alkalies  and  less  manganese. 
The  two  species  are  then  essentially  dimorphous  forms  of  the 
same  compound,  and  the  relation  between  them  is  made  all 
the  more  interesting  in  that  with  the  striking  differences  in 
physical  characters,  there  is  yet  an  obvious  relation  in  form. 
Dickinsonite  is  monoclinic  with  marked  pseudo-rhombohedral 
symmetry  and  of  fillowite  the  same  is  true  as  we  have  proved 
by  a  reexamination  of  fragments  parallel  to  the  distinct  but 
interrupted  basal  cleavage.  Moreover,  the  dimensions  of  the 
forms  show  a  close  relation,  thus  we  have  : 

Dickinsonite.  Fillowite. 

100  A  001  =  61°  30'  58°  31' 

001  A  221  =  61      8  58    40 

We  have  then  in  these  two  species  an  example  of  a  very 
close  and  interesting  case  of  dimorphism.  The  suggestion 
that  the  two  could  be  regarded  as  independent  forms  of  the 
same  mineral  differing  in  habit  and  state  of  aggregation  could 
not  possibly  be  made  by  one  who  had  seen  and  examined  the 
specimens.  We  have  still  hope  that  in  future  explorations 
at  Branchville  we  may  find  a  new  supply  of  this  rare  and 
interesting  species,  named  in  honor  of  our  good  friend,  Mr. 
A.  N.  Fillow. 

CONCLUSION  OF  THE  BRANCHVILLE  PAPERS. 


ON  THE  CHEMICAL  COMPOSITION  OF 
AMBLYGONITE. 

BY  SAMUEL  L.   PENFIELD. 
(From  Amer.  Jour.  Sci.,  1879,  vol.  18,  pp.  295-301.) 

THE  new  mineral  species  triploidite  described  by  Messrs. 
Brush  and  Dana*  is  shown  by  them  to  be  isomorphous  with, 
wagnerite  and  closely  related  in  composition  to  triplite. 
These  three  minerals  have  respectively  the  formulas  (Mn,Fe)3 
P2O8  +  (Mn,Fe)  (OH)2,  Mg3P2O8  +  MgF2  and  (Fe,Mn)3P2O8 
-f  (Fe,Mn)F2.  From  a  comparison  of  these  formulas  it  is 
argued,  page  60,  that  the  relation  between  the  minerals  re- 
quires the  assumption  that  the  hydroxyl  in  triploidite  must 
play  the  same  part  as  fluorine  in  the  other  two. 

In  this  paper  it  will  be  shown  that  in  amblygonite  the 
hydroxyl  group  is  also  isomorphous  with  fluorine,  and  that 
in  chemical  composition  the  original  amblygonite  does  not 
differ  from  the  American  and  Montebras  varieties  which  have 
been  called  hebronite.  It  will  also  be  shown  that  the  results 
of  the  analyses  require  the  adoption  of  a  new  formula  for 
the  mineral,  more  simple  than  that  previously  accepted.  For 
analysis  specimens  have  been  selected  from  three  localties 
in  Maine,  from  Branchville,  Connecticut,  where  the  mineral 
has  been  lately  discovered  by  Messrs.  Brush  and  Dana,  also 
two  varieties  from  Montebras  and  one  from  Penig,  Saxony, 
the  last  from  a  specimen  in  the  Yale  College  collection. 

The  analyses  are  arranged  so  as  to  form  a  series,  beginning 
with  the  one  which  contains  the  smallest  amount  of  water. 
The  results  of  the  analyses  may  be  tabulated  as  follows :  f 

*  Page  57. 

t  The  analyses  were  made  in  duplicate,  and  in  the  original  article  the 
results  of  all  the  determinations  are  given.  The  figures  here  given  are 
the  averages  of  duplicate  determinations  as  they  appeared  in  the  original 
article.  In  No.  IV.  the  P206  determination  was  lost,  and  the  result  given 
is  that  obtained  by  difference. — EDITOR. 


122 


THE   CHEMICAL   COMPOSITION 


I.  From  Penig,  Saxony. 

II.  From  Montebras,  France,  variety  A,  sp.  gr.  3.088. 

III.  From  Auburn,  Maine,  sp.  gr.  3.059. 

IV.  From  Hebron,  Maine,  variety  A. 
V.  From  Paris,  Maine,  sp.  gr.  3.035. 

VI.  From  Hebron,  Maine,  variety  B,  sp.  gr.  3.032. 

VII.  From  Branchville,  Connecticut,  sp.  gr.  3.032. 

VIII.  From  Montebras,  France,  variety  B,  sp.  gr.  3.007. 


A1208 


I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

48.24 
33.55 

47.09 
33.22 

48.48 
33.78 

[48.53] 
34.12 

48.31 
33.68 

47.44 

33.90 

48.80 
34.26 

48.34 
35.55 

8.97 

7.92 

9.46 

9.54 

.  9.82 

9.24 

9.80 

9.52 

2.04 

3.48 

0.99 

0.34 

0.34 
0.03 

0.66 

0.19 

0.33 

1.75 

2.27 

3.57 

4.44 

4.89 

6.05 

6.91 

6.61 

11.26 

9.93 
024 

6.20 

5.24 

4.82 

5.45 

1.75 

1.75 
0.35 

0.29 

0.13 

0.10 

105.94 
4.74 

104.15 
4.02 

102.48 
2.61 

102.21 
2.21 

101.89 
2.03 

101.74 
2.29 

101.10 
0.74 

100.45 
0.74 

Na20 

K20 

H2O 

F 

CaO 

Mn20g 


101.20    100.13      99.87     100.00      99.86      99.45    100.36      99.71 

For  more  easy  comparison  the  -  ratios  from  the  foregoing 
analyses  are  collected  in  the  following  table  by  themselves, 

where  R  equals  Li  and  Na. 


I. 
II. 
III. 

IV. 

v. 

VI. 

VII. 

VIII. 


p 

1.00 
1.00 
1.00 
1.00 
1.00 
1.00 
1.00 
1.00 


Al 
0.96 
0.97 
0.96 
0.97 
0.96 
0.98 
097 
0.96 


i 

B 

0.98 
0.98 
0.97 
0.95 
0.97 
0.95 
0.96 
0.96 


(OH,  F) 
1.16 
1.17 
1.06 
1.13 
1.17 
1.27 
1.09 
1.21 


It  will  be  seen  that  all  of  these  approach  closely  to  the 
ratio  1:1:1:1,  hence  A12P2O8  +  2R(OH,F)  is  proposed 
as  the  true  formula  for  all  varieties  of  this  mineral.* 

*  A  better  way  to  express  the  composition  of  the  mineral  is  to  regard  it 
as  containing  the  isomorphous  fluorine  and  hydroxyl  molecules,  Li[AlF] 
P04  and  Li [A10H]P04,  which  maybe  written Li[Al(F, OH)]  PO4.  —  EDITOR. 


OF  AMBLYGONITE.  123 

DesCloizeaux,  from  a  difference  in  optical  characters  made 
out  by  him,  has  divided  the  mineral  into  two  species :  the 
original  amblygonite,  including  I  and  II  in  the  foregoing  list ; 
and  a  second  species  for  which  he  proposed  the  name  monte- 
brasite  (hebronite  of  von  Kobell),  including  analyses  III  to 
VIII  above.  The  mineral  from  Branchville  has  not  been 
examined  optically  and  the  material  is  very  unfavorable  for 
such  an  examination.  Owing  to  the  close  identity  in  chemi- 
cal composition  it  seems  that  a  slight  variation  in  optical 
properties  is  hardly  sufficient  ground  for  dividing  the  min- 
eral into  two  species,  but  on  the  contrary  it  is  believed  that 
the  old  name  amblygonite  should  be  retained,  and  that  all 
varieties  should  be  included  by  it.  A  description  of  the 
method  of  analysis  is  here  omitted. 


ON  THE  CHEMICAL  COMPOSITION  OF 
CHILDRENITE. 

BY  S.  L.   PENFIELD. 
(From  Araer.  Jour.  Sci.,  1880,  vol.  19,  pp.  315-316.) 

AFTER  the  publication  by  Messrs.  Brush  and  Dana*  of  their 
paper  in  which  the  new  species,  eosphorite,  was  described  and 
shown  to  be  closely  related  both  physically  and  chemically  to 
childrenite,  they  proposed  to  me  to  make  a  new  investigation 
of  the  composition  of  the  latter  species  with  a  view  to  decid- 
ing the  uncertainty  in  regard  to  its  true  formula.  Professor 
Brush  very  kindly  provided  and  placed  at  my  disposal  a  speci- 
men out  of  his  collection  from  Tavistock.  From  this  the 
material  for  the  following  analysis  was  taken.  The  crystals 
were  small,  of  a  yellow-brown  color,  and  were  very  carefully 
picked  from  the  siderite  and  oxide  of  iron  with  which  they 
were  associated.  Only  lustrous  crystals  were  accepted,  and 
any  doubtful  material  was  discarded.  Between  eight  and 
nine  tenths  of  a  gram  were  thus  obtained.  Analysis  I  is  a 
complete  analysis  made  on  a  little  over  half  a  gram ;  it  was 
conducted  with  the  greatest  care  and  a  special  test  was  made 
for  alkalies,  so  that  they  might  be  determined  quantitatively 
if  present.  As  Church  in  his  analysis  found  iron  sesquioxide 
present,  the  remaining  three  tenths  of  a  gram  of  the  mineral 
were  tested  quantitatively  with  potassium  permanganate ;  the 
result  indicated  26.08  per  cent  of  FeO,  varying  only  0.12 
per  cent  from  gravimetric  determination  of  iron  protoxide  in 
the  same  portions ;  so  that  we  may  conclude  that  the  mineral 
really  contained  no  iron  sesquioxide.  After  titrating  with 
potassium  permanganate  the  solution  was  reserved,  and  P2O5, 

*  Page  48. 


CHEMICAL   COMPOSITION  OF  CHILDRENITE.        125 

A12O3  and  FeO  determined  in  it  gravimetrically  (analysis  II) 
as  a  control  on  the  other  analysis. 


i. 

ii. 

M 

f: 

ano  caicu. 
rom  analyi 

P205 

30.19 

29.98 

0.212 

1.00 

A1203 

21.17 

21.44 

0.208 

0.98 

FeO 

26.54 

26.20 

0.368  ) 

MnO 

4.87 

0.069  C  0.458 

2.16 

CaO 

1.21 

0.021  ) 

H20 

15.87 

0.882 

4.16 

Quartz 

0.10 

99.95 

The  above  ratio  corresponds  closely  to  the  following : 
P205  :  A1203  :  KO  :  H20  =  1  :  1  :  2  :  4  (R  =  Fe,  Mn,  and  Ca). 

This  gives  the  empirical  formula  R2A12P2O10 .  4H2O,  which 
may  be  written,  A12P2O8  -f  2R(OH)2  +  2  aq.,  the  same  as 
that  made  out  for  eosphorite. 

The  formula  in  this  case  corresponds  to  the  following 
percentage  composition :  P2O5  30.80,  A12O3  22.31,  FeO  26.37, 
MnO  4.87,  H2O  15.65  =  100.  This  agreed  satisfactorily  with 
analysis  I. 

NOTE.  —  The  water  in  eosphorite  is  wholly  driven  out  at  a 
very  low  temperature ;  hence  it  may  be  concluded  that  eosphor- 
ite and  childrenite  contain  water  of  crystallization  and  not 
hydroxyl.  The  general  formula  of  these  minerals  should  there- 
fore be  written  as  follows :  R[A10]P04  .  2H20.  In  eosphorite 
R  =  Mn  and  a  little  Fe,  in  childrenite  R  =  Fe  and  a  little  Mn. 
Both  contain  the  univalent  radical  [A10].  —  EDITOR. 


BASTNASITE   AND  TYSONITE   FROM  COLORADO. 

BY  O.  D.  ALLEN  AND  W.  J.   COMSTOCK. 
(From  Amer.  Jour.  Sci.,  1880,  vol.  19,  pp.  390-393.) 

THE  material  for  the  investigation  the  results  of  which  are 
here  given,  was  received  from  Messrs.  S.  T.  Tyson  and  H.  E. 
Wood,  to  whom  our  thanks  are  due. 

The  first  mineral  examined  was  found  by  careful  qualitative 
analysis  to  contain  only  the  metals  of  the  cerium  group,  fluorine, 
and  carbonic  acid,  with  a  trace  of  iron.  Its  characters  are  as 
follows :  Hardness  —  4-4.5.  Sp.  gr.  =  5.18,  5  .20.  Luster 
vitreous  to  resinous.  Color  reddish  brown.  Streak  light 
yellowish  gray.  Infusible.  It  is  very  slightly  attacked  by 
hydrochloric  acid,  without  perceptible  evolution  of  carbonic 
acid.  Strong  sulphuric  acid  dissolves  it  with  evolution  of 
carbonic  and  hydrofluoric  acids.  Strongly  heated  in  a  closed 
tube  shows  scarcely  a  trace  of  moisture.  The  direct  results 
obtained  by  analysis  are: 


Ce203 

(La,  Di)203 
C02 


By  converting  a  known  weight  of  the  mixed  oxides  of  the 
mineral  into  anhydrous  normal  sulphates,  the  joint  atomic 
weight  of  the  metals  was  found  to  be  140.2.  If  from  the 
carbonic  acid  obtained,  an  amount  of  the  bases  is  calculated 
sufficient  to  form  normal  carbonate,  the  remainder  of  the 
bases  calculated  as  metals  and  the  fluorine  estimated  by 
difference,  the  mean  becomes : 


I. 

n. 

,,                          Swedish  bastnasite 
by  Nordeiiskiold. 

40.88 
34.95 

41.21 
34.56 

££}»» 

28.49  ) 
45.77  ) 

74.26 

20.09 

20.20 

20.15 

19.50 

BASTNASITE  AND   TYSONITE.  127 

Ratio. 

(Ce,  La,  Di)203      50.13  0.153 

Ce,  La,  Di  21.82  0.155 

C02  20.15  0.458 

Fl  7.90  0.416 

100.00 
E203  :  E  :  C02  :  Fl  =  1  :  1.01  :  3  :  2.72, 

corresponding  to  the  formula 

R2F16  +  2R2(C03)3,* 

in  which  R  =  Ce,  La,  and  Di.  If  the  atomic  weight  of  R  = 
140.2,  as  found  in  the  present  case,  the  formula  requires : 

(Ce,  La,  Di)203      49.94 
Ce,  La,  Di  21.32 

C02  20.07 

Fl  8.67 

100.00 

This  mineral  corresponds  to  that  from  Sweden  described  by 
Hisinger  f  under  the  name  of  Basiskfluorcerium.  It  was  later 
reinvestigated  by  A.  E.  Nordenskiold,  J  who  first  ascertained 
its  correct  composition  and  called  it  hamartite.  Huot  had,  how- 
ever, previously  called  the  mineral  bastnasite,  after  the  locality. 
Nordenskiold's  analysis  is  given  above  for  comparison. 

Associated  with  bastnasite  occurs  a  mineral  which  proved  to 
be  an  anhydrous  normal  fluoride  of  cerium,  lanthanum,  and 
didymium,  which  we  have  examined  with  the  following  results : 

H  =  4.5-5.  Specific  gravity  =  6.14,  6.12. 

Luster  vitreous  to  resinous.  Color  pale  wax-yellow.  Streak 
nearly  white.  B.  B.  blackens  but  does  not  fuse.  In  closed 
tube  decrepitates,  the  color  changes  to  a  light  pink,  and 
shows  slight  traces  of  moisture.  Insoluble  in  hydrochloric 
and  nitric  acids,  but  dissolves  in  concentrated  sulphuric  acid 

*  The  formula  may  best  be  written,  [KF]C03,  R  =  Ce,  La  and  Di.  —  EDITOK. 
t  GEf .  Ak.  Stockh.,  1838,  p.  187.  J  CEf.  Ak.  Stockh.,  1868,  p.  399. 


128  BASTNASITE  AND   TYSONITE 

with  evolution  of  hydrofluoric  acid.  Qualitative  examination 
showed  only  the  presence  of  fluorine  and  the  metals  of  the 
cerium  group. 

Quantitative  analysis  gave  the  following  results : 

I.  II.  Mean.  Ratio. 

Ce                  40.16  40.22  40.19  -i- 141.2  =  0.284 j 

La,  Di           30.29  30.45  30.37  -7- 138     =  0.220  > 

Fl  (diff.)       29.55  29.33  29.44                                1.547 

100.00  100.00  100.00 

From  which  is  obtained  the  ratio 

B  :  Fl  =  1  :  3.07. 

The  formula  (Ce,  La,  Di)  F13  appears  therefore  to  express 
the  composition  of  the  mineral.  As  this  mineral  differs  essen- 
tially in  chemical  composition  and  physical  properties  from 
any  mineral  hitherto  described,  it  should  be  regarded  as  a  new 
species.  We  propose  for  it  the  name  tysonite. 

The  process  of  analysis  used  for  both  minerals  was  as 
follows :  a  solution  was  effected  by  strong  sulphuric  acid. 
After  removing  the  excess  of  sulphuric  acid  the  sulphates 
were  dissolved  in  water.  The  bases  were  precipitated  with 
ammonium  oxalate,  the  oxalates  ignited  in  air  and  finally  in 
hydrogen  in  order  to  remove  the  slight  amount  of  oxygen 
which  Di2O8  takes  upon  ignition  in  air.  The  cerium  in  the 
mixed  oxides  was  determined  volume  trie  ally  by  Bunsen's 
method.  The  CO2  was  determined  by  ignition  in  a  com- 
bustion tube  with  lead  chromate  mixed  with  a  little  fused 
potassium  dichromate.  A  trial  of  this  method  with  pure 
calcium  carbonate  mixed  with  calcium  fluoride  gave  satis- 
factory results. 

Locality  and  mode  of  occurrence.  —  The  material  first  fur- 
nished to  us  by  Messrs.  Wood  and  Tyson  came  from  a  locality 
at  that  time  unknown  to  them,  and  consisted  of  a  few  grams 
of  fragments  of  crystals  of  bastnasite,  to  some  of  which  were 
attached  portions  of  the  tysonite,  readily  distinguishable  by 
its  lighter  color  and  perceptible  cleavage,  which  is  wholly 


FROM  COLORADO.  129 

lacking  in  the  bastnasite.  Mr.  Tyson,  having  recently  suc- 
ceeded in  reaching  the  locality,  which  is  near  Pike's  Peak,  has 
just  placed  in  our  hands  for  examination  all  the  specimens 
which  he  could  obtain,  about  a  dozen  crystals  and  frag- 
ments of  crystals,  the  largest  of  which  are  upwards  of  an 
inch  in  diameter,  mostly  free,  but  in  some  cases  attached  to 
feldspar. 

The  crystals  are  hexagonal  in  form,  the  only  planes  observed 
being  c  (0001),  m  (1010)  and  a  (1120).  On  a  single  crystal 
can  be  seen  the  remains  of  pyramidal  planes,  but  so  rounded 
by  abrasion  that  any  measurements  would  be  useless.  The 
crystals  are  prismatic  in  habit,  the  smaller  ones  slender  and 
somewhat  elongated,  the  larger  ones  short  and  thick. 

These  specimens  show  an  interesting  relation  between  the 
fluoride  and  the  fluo-carbonate.  The  smaller  crystals  consist 
wholly  of  fluo-carbonate ;  in  the  larger  crystals,  however, 
a  portion  occupying  the  interior,  about  equally  distant  from 
the  basal  planes,  usually  about  half  an  inch  from  them 
and  extending  nearly  to  the  lateral  planes,  consists  of  the 
fluoride.  The  thickness  of  this  band  varies  with  the  length 
of  the  crystals  from  a  few  lines  to  half  an  inch.  The  line 
of  demarkation  between  it  and  the  fluo-carbonate  is  quite 
distinct.  This  mode  of  occurrence  of  the  two  compounds, 
being  such  as  is  often  seen  in  crystals  which  have  undoubtedly 
undergone  partial  changes  of  composition,  leads  to  the  conclu- 
sion that  the  bastnasite  of  Colorado  was  formed  by  a  change 
of  a  fluoride  into  a  fluo-carbonate.  In  the  fluoride  a  distinct 
but  not  strongly  marked  cleavage  exists  parallel  to  the  basal 
planes  of  the  inclosing  fluo-carbonate.  In  the  latter  we  could 
detect  no  evidence  of  cleavage. 


CRYSTALLIZED  TIEMANNITE  AND  META- 
CINNABARITE. 

BY  SAMUEL  L.  PENFIELD. 
(From  Amer.  Jour.  Sci.,  1885,  vol.  29,  pp.  449-454.) 

1.  TIEMANNITE. 

IN  October  last,  Professor  J.  E.  Clayton,  president  of  the 
Salt  Lake  Mining  Institute,  sent  to  Professor  Brush  a  few 
specimens  containing  crystals  of  a  selenide  of  mercury  which 
were  suitable  both  for  analysis  and  measurement.  The  speci- 
mens were  from  Marysvale,  Southern  Utah,  the  same  locality 
which  afforded  the  sulpho-selenide  of  mercury,  onofrite,* 
described  by  Professor  Brush.  A  description  of  the  occur- 
rence of  the  mineral,  as  stated  by  Prof.  Clayton,  is  given  at 
the  end  of  this  article,  and  I  take  great  pleasure  in  here 
expressing  to  him  my  thanks  for  calling  our  attention  to  these 
most  interesting  crystals. 

The  crystals  are  black,  with  high  metallic  luster  and  black 
streak ;  hardness  about  3 ;  specific  gravity  taken  twice  on  a 
chemical  balance  8.188-8.187;  fracture  conchoidal;  very 
brittle  and  with  no  apparent  cleavage. 

An  analysis  was  made  by  decomposing  the  mineral  in  a 
current  of  chlorine  gas,  precipitating  the  mercury  as  sub- 
chloride  by  means  of  phosphorous  acid  and  the  selenium  with 
sulphurous  anhydride.  The  results  are  given  below  with  the 
determinations  of  small  amounts  of  sulphur,  cadmium  and 
insoluble  residue. 

*  Amer.  Jour.  Sci.,  1881,  vol.  21,  p.  312. 


TIEMANNITE  AND  METACINNABARITE. 


131 


Ratio. 

Se 

29.19 

0.369 

S 

0.37 

0.012 

Hg 

69.84 

0.349 

Cd 

0.34 

0.003 

Insol. 

0.06 

1.00 
0.92 


99.80 

The  ratio  of  the  selenium  plus  sulphur  to  the  metals  is  1 :  0.93 
or  nearly  1  :  1,  as  required  by  a  normal  selenide,  and  as  the 
impurities  are  present  only  in  very  small  quantities  the  min- 
eral may  be  regarded  as  a  simple  selenide  of  mercury.  The 
analysis  agrees  more  closely  with  the  theoretical  requirements 
than  any  previously  published,  which  may  be  in  consequence 
of  the  greater  purity  of  the  crystallized  material. 

The  crystals  measure  up  to  3  mm.  in  diameter.  They  are 
isometric,  tetrahedral,  and  the  habit  of  the  few  at  my  disposal 
is  quite  various.  The  plus  and  minus  tetrahedrons  are 
usually  about  equally  developed  and  vary  in  luster ;  the  cubic 
faces  are  also  prominent  and  are  at  times  striated  diagonally 
parallel  to  their  intersection  with  the  dullest  tetrahedron  and 


FIGURE  1. 

most  developed  tristetrahedron  forms.  Twins  with  o  as  the 
twinning-plane  are  common.  Taking  the  forms  of  the  most 
developed  tristetrahedron  as  positive,  the  observed  forms  are 
as  follows:  0(111),  usually  dull,  o'(Ill)  lustrous,  a(100), 
w(oll)  and  </>(733).  The  above  forms  were  all  observed  on 
one  twin  crystal,  Figure  1,  the  latter  <£,  as  a  very  small  face 
but  giving  distinct  reflections.  The  faces  in  both  halves  of 


132  CRYSTALLIZED   TIEMANNITE 

the  twin  crystal  figured  are  lettered  alike  except  that  those 
in  twin  position  are  underscored.  Twins  on  the  specimens  in 
my  possession  are  more  common  than  single  crystals,  some 
of  them  showing  simply  both  tetrahedrons  and  cube. 

The  measured  angles  are  the  following,  the  mean  of  closely 
agreeing  results  being  given : 

Observed.  Calculated. 

o  A  o',  111  A  Til  =  70°  31'  70°  32' 

a  A  </,  001  A  Til  =  54°  45'  54°  44' 

a  A  (o,  001  A  115  =  *gl  ^  1         15°  48' 
a  A  <#»,  001  A  337  =  31°  10'  31°  13' 

A  number  of  crystals  have  the  habit  shown  in  Figure  2 ; 
only  one  was  lustrous  enough  to  admit  of  measurement.  The 
zone  a,  6,  c,  etc.,  was  very  much  striated  and  distorted  through 
oscillatory  combination,  but  by  turning  the  crystal  so  as  to 
catch  the  light  reflected  from  it,  it  could  be  readily  seen  to 
consist  of  several  distinct  forms.  On  the  reflecting  goniometer 
the  signal  was  reflected  from  the  faces  in  almost  an  unbroken 
band ;  a  few  of  the  most  prominent  reflections,  however,  were 
recorded  and  are  given  below.  The  reflection  from  the  faces 
of  a  lamplight  placed  at  a  distance  across  a  large  room  was 
resorted  to,  all  the  faces  of  like  inclination  reflecting  together 
and  yielding  a  sort  of  "  schimmer  Messung ; "  the  results  of 
which,  although  not  very  exact,  being  sufficiently  so  to  fix  the 
symbols  of  the  different  forms.  The  measurements  taken  on 
both  sides  of,  and  measured  from,  the  cubic  face  a,  are  given 
below. 

be  e  w  m  <f> 

Direct  reflection      6°  11'     9°  17'      12°  30'  ) 

6°  17'     9°  24'      12°  42'      17°  17' 


^6°  25'     9049'      12058'      17°  16' 
Direct  reflection      6°  12'  \ 

6°    7'     9°  17'     12°  20'     16°  26'     25°  7'     31°  23'  >  left. 


Schimmer      ]  50  5(y  90  2'  11°  47'  16°  20'  25°   

Mean  .      .  6°  10'  9°  22'   12°  27'   16°  47'  25°  3'  31°  23' 


AND  METACINNABARITE.  133 

Calculated  for  the  following  forms  : 

001  A  1.1.13  =    6°  13'  001  A  115  =  15°  48' 

001  A  2.2.17  =    9°  27'  001  A  113  =  25°  14' 

001  A  2.2.13  =  12°    6'  001  A  337  =  31°  13' 

The  reflections  from  <u,  m  and  <£  were  very  faint,  that  from  (/> 
being  the  last  trace  of  reflected  light  which  could  be  seen  on 
turning  the  crystal.  The  measurements  agree  quite  well 
among  themselves,  considering  the  method  used,  and  warrant 
my  taking  the  above  symbols  according  to  which  Figure  2  is 
drawn.  The  form  o>(511)  shows  the  greatest  variation,  but, 
as  it  is  a  prominent  form  on  the  simpler  and  more  perfect 
crystals,  it  seems  better  to  regard  the  variation  as  due  to  error 
in  measurement  than  to  take  the  less  probable  symbol  (922) 
with  calculated  value  17°  27'.  The  only  other  form  m'(3ll) 
was  quite  large  and  very  strongly  striated  parallel  to  its  com- 
bination edge  with  the  cube.  The  faces  gave  no  reflection  but 
were  measured  by  covering  them  with  glass  plates  and  then 
measuring  on  the  cube.  This  was  repeated  twice,  giving 
24°  49',  25°  21',  calculated  25°  14'. 

In  appearance  the  crystals  resemble  very  closely  those  of 
sphalerite,  while  the  forms  which  are  common  to  both  are 
a(100),  o(lll),  o'(lll),  <»(511),  and  w(311). 


NOTE.     The  second  portion  of  this  article  relating  to  Metacin- 
nabarite  is  here  omitted.  —  EDITOR. 


GERHARDTITE  AND  ARTIFICIAL  BASIC  CUPRIC 

NITRATES. 

BY  H.  L.  WELLS  AND  S.  L.  PENFIELD. 
(From  Amer.  Jour.  ScL,  1885,  vol.  30,  pp.  50-57.) 

WE  shall  describe  in  the  present  article  a  natural,  crystallized 
basic  cupric  nitrate  and  a  crystallized  artificial  salt  of  the  same 
chemical  composition  but  of  different  crystalline  form.  We 
also  give  an  account  of  a  reinvestigation  of  two  basic  cupric 
nitrates  to  which  have  been  ascribed  different  compositions, 
but  which,  as  we  shall  show,  have  the  same  composition  as  the 
basic  nitrates  described  by  us  and  by  other  investigators,  whose 
results  will  be  briefly  summarized. 

GERHARDTITE,  a  new  mineral. 

This  mineral  was  first  identified  as  a  new  species  by  Pro- 
fessor Brush,  who  found  it  among  a  lot  of  copper  minerals 
from  the  United  Verde  Copper  Mines,  Jerome,  Arizona,  which 
were  left  at  the  Sheffield  Scientific  School  by  Mr.  G.  W. 
Stewart,  assay er,  from  that  place. 

The  single  specimen  in  our  possession  consists  of  a  small 
piece  of  very  pure  massive  cuprite,  along  a  crack  in  which  the 
crystals  of  the  nitrate  occur,  together  with  acicular  crystals 
of  malachite.  The  crystals,  4-6  mm.  in  diameter,  were  few  in 
number  and  were  almost  wholly  sacrificed  to  obtain  material 
for  investigation.  An  attempt  has  been  made  to  obtain  more 
of  the  material,  but  as  yet  no  other  specimens  have  been 
received,  although  we  are  in  hopes  that  more  may  be  found  at 
the  locality.  From  the  abundance  of  crystals  on  the  specimen 
in  our  possession,  it  would  seem  that  there  must  have  been  a 
quantity  of  it  found.  It  was  probably  regarded  as  malachite  by 
the  miners.  Another  specimen  contains  crystals  of  atacamite 
on  the  cuprite. 


GERHARDTITE.  135 

The  crystals,  which  were  carefully  separated  from  the  cuprite, 
were  subjected  first  to  crystallographic,  then  to  chemical  exam- 
ination. About  0.8  of  a  gram  was  obtained  almost  perfectly 
pure,  the  only  impurity  being  a  few  acicular  crystals  of  mala- 
chite which  sometimes  penetrated  the  nitrate  but  were  visible 
only  under  the  microscope. 

The  hardness  of  the  mineral  is  2.  Specific  gravity,  3.426. 
Color  dark-green.  Streak  light-green.  Transparent. 

The  crystals  after  being  detached  were  only  fragmentary. 
All  those  suitable  for  measurement  were  reserved.     They  were 
very  fragile  and  had  to  be  separated  and  handle  dwith  very  great 
care.     The  crystals  are  orthorhom- 
bic,  having  the  habit  shown  in  the 
accompanying    figure.      There   are 
two  cleavages,  which  serve  for  orien- 
tation, one  basal,  parallel  to  <?,  as 
perfect  as  the  most  perfect  cleavage 
of  gypsum,  a  second,  less  perfect, 

parallel  to  the  micropinacoid.  The  crystals  can  be  readily  bent, 
in  which  case  they  crack  and  separate  along  the  latter  direction. 
The  most  prominent  forms  on  the  crystals,  besides  the  basal 
plane,  are  a  series  of  pyramids  occurring  in  oscillatory  com- 
bination, which  makes  their  identification  somewhat  difficult. 
The  best  measurements  were  obtained  from  a  small  but  very 
perfect  macrodome  which  was  found  on  two  crystals.  Owing 
to  the  fragmentary  nature  of  the  crystals  and  the  difficulty  of 
identifying  the  pyramidal  planes,  their  orthorhombic  form 
might  be  doubted  were  it  not  for  their  optical  properties. 

The  axial  ratio  was  obtained  from  the  following  measure- 
ments : 

c  A  z  001  A  201  =  68°  16'  00" 
ZAP  201  A  111  =  39°    3'  30" 
giving 

a  :  b  :  c  =  0.92175  :  1  :  1.1562 

The  following  forms  were  observed : 

c,     001         r,    551        t,       778  w,        223 

z,     201        s,    221        M,      334  x,     13.13.20 

m,   110        p,    111         v,     7.7.10          y,         112 


136  GERHARDTITE. 

The  following  is  the  table  of  measured  and  calculated 
angles,  the  measurements  being  made  on  eight  crystals,  the 
number  of  times  each  form  was  measured  being  given. 

Calculated.  Measured.  No.  of  times. 

m  A  m  110  A  110  85°  20' 

z  A  z  201  A  201  43°  28'  43°  34'  1 

c  A  m  001  A  110  90°  00'  90°  15'-90°  25'  2 

c  A  r  001  A  551  83°  19'  83°    1'  1 

CAS  001  A  221  73°  40'  73°  53'  1 

CAP  001  A  111  59°  37'  59°  23'-59°  57'  6 

c  A  t  001  A  778  56°  11'  55°  57/-56°  19'  3 

CAM  001  A  334  51°  W  51°  52/-52°  20'  2 

CAW  001  A  7.7.10  50°    3'  49°  46'-50°  38'  3 

CAW  001  A  223  48°  40'  48°    8'-49°  12'  8 

c  A  x  001  A  13.13.20  47°  57'  47°  ir-47°  56'  5 

c  A  y  001  A  112  40°  28'  40°  13'-40°  18'  2 

x  AX       13. 13. 20  A  13.13.20  60°  27'  60°    9'  1 

Only  distinct  reflections  were  recorded,  though  other  forms 
seemed  to  be  present  but  were  not  definite  enough  to  be  deter- 
mined. The  variation  in  the  measurements  is  large  and  may 
be  due  in  part  to  an  accidental  bending  of  the  crystals.  The 
forms  x  and  v  with  improbable  indices  would  have  been 
regarded  as  accidental  had  they  not  occurred  repeatedly  giving 
very  distinct  reflections. 

Tabular  fragments  parallel  to  the  basal  cleavage,  show 
under  the  polarizing  microscope  an  extinction  parallel  to  the 
macro-diagonal  cleavage  lines,  and  in  convergent  light  a 
bisectrix  normal  to  £,  001.  The  optic  axes  lie  in  the  brachy- 
pinacoid.  The  axial  angle  is  large  and  could  not  be  measured 
in  air.  Measured  in  the  heavy  solution  of  HgI2  in  KI  (n  — 
1.708  for  yellow,  1.722  for  green)  : 

2H  =  76°  20'  for  yellow. 
2H  =  80°    4' for  green. 
Dispersion  p<v. 

A  very  thin  section  had  to  be  used  to  obtain  the  character  of 
the  dispersion,  as  moderately  thick  sections  were  practically 
opaque  to  yellow  light.  The  indices  of  refraction  could  not  be 
determined  owing  to  the  want  of  suitable  material,  the  Kohl- 
rausch  Totalreflectometer  giving  no  total  reflection. 


BASIC  CUPRIC  NITRATES.  137 

Double-refraction  is  strong,  negative. 
Pleochroism  is  distinct : 

For  vibrations  parallel  to  t  (that  is  a),  blue. 
For  vibrations  parallel  to  fc  (that  is  5),  green. 
For  vibrations  parallel  to  a   (that  is  c),  green. 

Chemical  composition.  —  Qualitative  examination  showed 
only  the  presence  of  CuO,  N2O5  and  H2O.  An  analysis  by 
Wells  gave  the  following  results : 

I.   0.3975  gram  yielded  0.0457  H20  and  0.2634  CuO. 
II.   0.3986  gram  yielded  0.0449  H20,  0.2646  CuO,  and  19.7  c.c. 
dry  N  at  12.8°  and  759  mm.  (cor.). 


H20 

CuO 


Found.                             Calculated  for 
I.                           II.             4CuO  .  N205  .  3H20. 

11.49 

11.26 

11.56 

66.26 

66.38 

66.22 

22.25* 

22.76 

22.52 

100.00          100.40          100.00 


Pyrognostics,  $c.  B.  B.  fuses  at  2,  coloring  the  flame  green. 
With  soda  on  coal  easily  reduced  to  metallic  copper  with  de- 
flagration. In  closed  tube  gives  nitrous  fumes  and  water 
which  reacts  strongly  acid.  Soluble  in  dilute  acids,  insoluble 
in  water. 

It  is  somewhat  surprising  that  a  mineral  of  this  composition 
has  not  been  found  before,  owing  to  the  occurrence  of  nitrates 
in  natural  waters,  the  stability  and  insolubility  of  the  com- 
pound, and  the  ease  with  which  it  is  made  artificially. 

We  propose  for  this  beautiful  and  unique  mineral,  the  only 
insoluble  nitrate  yet  found  in  nature,  the  name  Gerhardtite 
from  the  chemist  who  first  determined  the  true  composition 
of  the  same  compound  f  made  artificially. 

NOTE.  —  The  description  of  crystallized  artificial  basic  cupric 
nitrate  is  here  omitted.  —  EDITOR. 

*  By  difference.  t  Jour.  Pr.  Chem.,  xxxix,  136. 


ON  THE  CHEMICAL  COMPOSITION  OF 
HERDERITE. 

BY  S.  L.  FENFIELD  AND  D.  N.  HARPER. 
(From  Amer.  Jour.  Sci.,  1886,  vol.  32,  pp.  107-110.) 

THE  rare  material  for  carrying  on  the  present  investigation 
of  herderite  was  given  to  us  by  Mr.  L.  Stadtmiiller  and  Pro- 
fessor George  J.  Brush.  The  crystals  were  carefully  picked 
by  hand  and  freed  as  far  as  possible  from  all  foreign  matter. 
They  were  then  crushed  and  sifted  and  suspended  in  the 
Thoulet  solution;  only  the  material  whose  specific  gravity 
was  greater  than  2.95  was  used  for  analysis.  By  this  means 
there  was  separated  from  the  hand-picked  crystals  a  little 
questionable  material,  which  was  used  in  making  a  sort  of 
preliminary  analysis,  and  we  were  able  to  obtain  over  five 
grams  of  very  pure  material.  Before  making  the  separation 
with  the  Thoulet  solution  we  carefully  took  the  specific  grav- 
ity of  some  of  the  purest  crystals  by  taking  the  specific  gravity 
of  the  solution  in  which  they  were  suspended  without  floating 
or  sinking.  This  we  found  to  be  from  3.012  to  3.006,  the 
heaviest  being  the  specific  gravity  of  a  very  clear  transparent 
crystal,  while  the  more  opaque  and  cracked  crystals  were  a 
trifle  lighter.  The  mineral  is  so  much  heavier  than  the 
quartz  and  feldspar  to  which  the  crystals  were  attached,  that 
we  feel  very  confident  of  the  purity  of  the  material  which 
we  analyzed. 

The  analysis  was  made  after  we  had  had  considerable 
experience  in  the  determination  of  beryllium  and  had  made 
some  experiments  in  determining  it  in  presence  of  phosphoric 
acid.  The  method  which  we  adopted  gave  good  satisfaction, 
and  we  give  it  here  somewhat  in  detail.  The  mineral  was 
dissolved  in  nitric  acid,  the  solution  concentrated  to  a  small 


CHEMICAL   COMPOSITION  OF  HERDERITE.         139 

volume,  sulphuric  acid  was  added,  and  the  gypsum  crystals, 
after  being  collected  by  filtering  through  a  rubber  funnel,  were 
ignited  and  weighed  as  CaSO4.  The  filtrate  was  concentrated 
in  a  platinum  dish  and  gently  ignited  to  drive  off  all  hydro- 
fluoric acid  and  the  excess  of  sulphuric  acid.  The  residue 
was  dissolved  in  hydrochloric  acid,  a  basic  acetate  precipitation 
of  a  part  of  the  beryllium  and  phosphoric  acid  was  made  in 
the  cold  with  ammonium  acetate,  and  a  little  calcium 
precipitated  from  the  acetic  acid  nitrate  by  ammonium  oxalate, 
which  was  ignited  and  weighed  as  CaO.  The  beryllium  in 
the  filtrate  from  calcium  oxalate  was  precipitated  as  a 
phosphate  by  means  of  ammonia,  filtered,  and  the  phosphoric 
acid  in  the  filtrate  precipitated  with  magnesia  mixture.  The 
two  precipitates  containing  the  beryllium  as  phosphate  (the 
basic  acetate  precipitate  contained  the  bulk  of  the  beryllium) 
were  ignited  in  the  same  crucible  and  fused  with  sodium 
carbonate.  The  fused  material  was  soaked  out  in  water, 
phosphoric  acid  obtained  in  the  solution  by  the  usual  method, 
while  the  insoluble  beryllium  oxide  was  dissolved  in  hydro- 
chloric acid,  precipitated  with  ammonia,  weighed,  and  the 
trace  of  P2O5  contained  in  it  separated  with  ammonium 
molybdate.  The  P2O5  and  bases  in  Analysis  III,  on  which 
we  place  the  greatest  confidence,  were  separated  and  determined 
in  the  above  manner. 

Other  determinations  are  given  to  show  the  accuracy  of  the 
method.  The  CaO  in  II  was  all  obtained  in  the  nitrate  from 
the  basic  acetate  precipitation  and  was  not  partially  precipitated 
as  gypsum.  The  BeO  in  the  same  analysis  was  tested  for 
A12O3,  but  not  more  than  a  questionable  trace  could  be 
detected.  The  P2O5  in  I  was  from  a  direct  determination 
with  ammonium  molybdate,  but  a  very  slight  mechanical  loss 
was  incurred.  The  fluorine  was  determined  in  III  by  driving 
off  the  silicon  fluoride  and  titrating  the  hydrofluosilicic  acid 
by  means  of  a  standard  alkali.*  After  making  the  determina- 
tions, fresh  U-tubes  were  connected  with  the  apparatus  and 
the  aspiration  carried  on  for  several  hours,  but  no  more 
*  Am.  Chem.  Jour.,  i,  27. 


140         CHEMICAL   COMPOSITION  OF  HERDERITE. 

silicon  fluoride  was  driven  off.  As  our  alkali  had  just  been 
standardized  by  means  of  sodium  carbonate  and  test  experiments 
on  fluor  spar,  we  feel  very  confident  that  the  fluorine 
determination  is  correct.  The  water  determinations  are 
somewhat  surprising.  Mackintosh  *  made  no  tests  for  water, 
and  considered  the  mineral  to  be  an  anhydrous  phosphate  with 
fluorine.  Winklerf  made  no  determination  of  fluorine  and 
obtained  no  satisfactory  tests  for  that  element  by  etching 
glass.  He  obtained  a  loss  by  ignition,  however,  of  6.59  per 
cent  in  the  Stoneham  mineral  by  strong  ignition,  which  he 
regards  as  water.  Genth  J  obtained  6.04  per  cent  of  fluorine 
by  direct  determination,  and  0.61  per  cent  of  water  by  heating 
the  mineral  with  lead  oxide  to  bright  redness.  Mackintosh  § 
obtained  good  tests  for  fluorine  by  etching,  and  found  a  loss  of 
6.03  per  cent  by  strong  ignition.  He  proved  conclusively  that 
fluorine  was  given  off  by  strong  ignition,  and  concludes  that 
it  is  replaced  in  part  at  least  by  oxygen.  We  are  scarcely 
willing  to  believe  that  such  a  reaction  would  take  place  on 
heating  an  anhydrous  phosphate  containing  fluorine.  Our 
first  water  determination  was  made  by  weighing  out  the 
mineral  in  a  boat,  placing  it  in  a  combustion  tube  containing  a 
layer  of  dry  sodium  carbonate,  igniting  the  tube  to  full  redness 
and  collecting  the  water  in  a  weighed  chloride  of  calcium  tube. 
We  obtained  0.69  per  cent;  afterward  the  mineral  was  dis- 
solved, and  analysis  II  completed  from  the  same  material. 
After  almost  completing  our  analysis  and  finding  only  5.27 
per  cent  of  fluorine  we  tried  the  following  experiments.  A 
little  herderite  powder  was  heated  in  a  closed  tube  of  hard 
glass;  at  first  only  a  slight  film  of  water  condensed  in  the 
cold  part  of  the  tube ;  by  strong  ignition  over  the  blast 
lamp,  however,  there  was  a  sudden  evolution  of  hydrofluoric 
acid,  which  etched  the  glass  very  perceptibly  near  the  mineral 
and  deposited  a  film  of  silica  and  very  acid  water,  as  marked 

*  Amer.  Jour.  Sci.,  1884,  vol.  27,  135. 
t  Neues  Jahrbuch  fur  Mineralogie,  1884,  ii,  134. 
J  Proc.  Amer.  Phil.  Society,  xxi,  1884,  694. 
§  Ainer.  Jour.  Sci.,  1884,  vol.  28,  p.  401. 


CHEMICAL   COMPOSITION  OF  HERDERITE.         141 

as  in  an  ordinary  reaction  for  fluorine  in  a  closed  tube  with 
acid  sulphate  of  potash.  In  our  experience  we  have  never 
seen  any  hydrous  fluoride  which  gives  off  such  strongly  acid 
water  and  such  a  marked  fluorine  reaction.  Some  of  the 
powdered  mineral  was  placed  in  a  closed  glass  tube,  covered 
with  a  layer  of  dry  sodium  carbonate  and  strongly  ignited; 
neutral  water  was  given  off  and  condensed  as  a  ring,  which 
indicated  more  than  a  trace  of  water.  The  water  was  obtained 
in  the  following  way.  About  two  grams  of  calcite  were 
ignited  over  the  blast  lamp  till  a  constant  weight  was  obtained. 
The  mineral  was  then  weighed  into  the  same  crucible,  the 
lime  was  slaked  with  water,  the  contents  of  the  crucible  were 
carefully  dried  and  then  ignited  till  constant  weight  was 
obtained,  the  water  being  calculated  from  the  loss  of  weight. 
The  slaking  of  the  lime  makes  an  intimate  mixture  of  the 
mineral  with  the  lime,  and  a  preliminary  experiment  proved 
to  us  that  only  neutral  water  was  driven  off.  In  I  there  was 
a  slight  mechanical  loss  in  slaking  the  lime,  which  caused 
the  water  determination  to  be  too  high,  the  P2O5  too  low. 
In  III  the  water  was  obtained  from  a  larger  quantity  of 
mineral.  No  sublimate  was  formed  on  the  cover  of  the 
crucible  by  the  volatilization  of  any  fluoride.  The  analyses 
were  made  on  air-dry  powder  which  lost  0.10  per  cent  by 
drying  for  one  hour  at  100°  C.  The  beryllium  precipitates 
were  always  of  a  light  cream  color  after  ignition,  indicating 
that  not  more  than  a  minute  trace  of  iron  was  present. 

The  following  quantities  of  mineral  were  used  in  making 
the  analyses:  I,  0.4552  grams;  II,  1.0029;  III,  P2O6  and 
bases  0.7336,  F.  0.9692,  H2O  1.1612. 

I.               II.  HI.                     Ratio.                             Calculated. 

P205        43.47  .  .  .  43.74  0.308  1.00        43.83 

BeO          .  .  .  15.28  15.51  0.620  2.01        15.44 

CaO  33.61  33.67  0.601  1.95        34.57 


F              5.27-f-38  0.138)                               5.86 

H20          4.37  ?      ...          3.70  0.205 )                              2.77 

101.89  102.47 

O  equivalent  of  F  .  .  .          2.22  2.47 

99.67  100.00 


142         CHEMICAL   COMPOSITION  OF  HERDERITE. 

The  ratio  of  P2O6  :  BeO  :  CaO  :  (F2  +  H2O)  =  1:2:2:1 
nearly.  The  high  temperature  at  which  the  water  is  driven 
off  indicates  that  it  is  not  water  of  crystallization,  but  is  very 
firmly  united  in  the  mineral  as  hydroxyl.  Every  H2O 
represents  two  hydroxyl  groups,  and  the  OH  is  isomorphous 
with  F.  The  ratio  of  F  :  OH  is  nearly  1  :  1,  or  more  nearly 
3  :  4  in  our  analysis.  In  the  calculated  analysis  we  have  used 
the  ratio  F  :  OH  =  1  :  1,  but  recognize  that  it  is  probably 
simply  a  case  of  isomorphism.  The  composition  of  herderite 
is,  therefore,  an  isomorphous  mixture  of  CaBeFPO4  with 
CaBe(OH)PO4.  This  may  be  written  CaBe(F,OH)PO4,  or 
a  salt  of  phosphoric  acid,  two  of  whose  hydrogen  atoms  have 
been  replaced  by  a  bivalent  element,  and  the  third  likewise  by 
a  bivalent  element  whose  other  free  affinity  has  been  satisfied 
by  a  fluorine  atom  or  hydroxyl.  This  is  the  same  composition 
as  that  proposed  by  Mackintosh,  except  that  he  regarded  the 
mineral  as  simply  the  fluorine  compound  and  did  not  detect 
the  water.  Chemically  herderite  is  closely  related  to  the 
three  minerals  —  wagnerite,  triplite,  and  triploidite,  whose 
compositions  are  respectively  Mg2FPO4,  (Fe,Mn)2FPO4  and 
(Fe,Mn)2(OH)PO4.  These  three  minerals  offer  the  best 
illustration  we  have  of  the  isomorphism  of  F  and  OH,  and 
we  feel  that  we  have  in  herderite  another  strong  proof  of  the 
correctness  of  this  interesting  relation. 


ON  THE  CHEMICAL  COMPOSITION  OF 
RALSTONITE. 

BY  S.  L.  PENFIELD  AND  D.  N.   HARPER. 
(From  Amer.  Jour.  Sci.,  1886,  vol.  32,  pp.  380-385.) 

A  NUMBER  of  years  ago  Professor  George  J.  Brush  generously 
gave  one  of  us  a  specimen  containing  a  large  amount  of  the 
rare  mineral  ralstonite  associated  with  thomsenolite  from 
Arksuk-fiord,  Greenland.  Considerable  time  was  spent  in 
picking  out  the  octahedral  crystals  free  from  thomsenolite, 
and  only  a  partial  analysis  was  made  which  was  never  pub- 
lished ;  difficulty  was  found  in  determining  the  fluorine,  and 
the  material  was  exhausted  before  a  complete  analysis  was 
made.  The  results  were  essentially  the  same  as  those  of 
Nordenskiold.*  Since  then  J.  Brandlf  has  analyzed  the 
mineral,  using  material  which  was  selected  by  Professor  P. 
Groth.  The  results  of  the  three  analyses  are  as  follows : 

Nordenskiold.  Penfield.  Brandl. 

Mg  5.52  4.29  3.56 

Na  5.66  4.12  5.50 

K  tr.  0.11 

Ca  1.99  1.67  1.53 

Al  22.94  22.33  22.14 

H2O  14.84  18.41  10.00 

F  57.12 


49.95  99.85 

Only  small  quantities  were  used  in  making  the  above 
analyses  owing  to  the  scarcity  of  material  and  the  difficulty 
of  obtaining  it  free  from  thomsenolite.  As  far  as  the  metals 
are  concerned,  the  three  analyses  agree  remarkably  well  with 

*  Geol.  Foren.  i  Stockholm.  Forhandl.,  1874,  ii,  81. 
t  Annalen  der  Chemie,  ccxiii,  7. 


144        CHEMICAL   COMPOSITION  OF  RALSTONITE. 

one  another.  Nordenskiold  calculated  that  the  50.05  per  cent 
of  material  which  was  not  determined  in  his  analysis,  if  as- 
sumed to  be  fluorine  would  not  be  sufficient  to  satisfy  all  the 
metals,  and  concludes  that  the  mineral  must  contain  some 
oxygen.  The  same  would  be  true  in  Penfield's  analysis. 
Brandl  determined  the  fluorine  directly  and  found  it  just 
sufficient  to  satisfy  the  metals;  he  proposed  the  formula 
3(Na2,Mg,Ca)F2 .  8A1F8 .  6H2O. 

The  fragments  which  were  left  after  selecting  material  for 
the  above  analysis  by  Penfield  were  carefully  saved,  and 
although  we  could  see  that  they  contained  large  quantities 
of  ralstonite,  still  it  was  found  impossible  to  separate  the 
pure  mineral  from  thomsenolite  by  hand  picking.  After 
selecting  the  purest  crystal  of  ralstonite  we  could  find,  we 
took  its  specific  gravity  by  just  floating  it  in  the  Thoulet 
solution  and  found  it  to  be  2.560 ;  by  the  same  method  we 
found  the  specific  gravity  of  cryolite  to  be  2.974  and  thom- 
senolite 2.979.  The  great  difference  in  specific  gravity 
between  ralstonite  and  the  other  two  minerals  admits  of  a 
very  perfect  separation  by  means  of  the  Thoulet  solution. 
All  the  material  which  we  had  was  crushed  and  made  to  pass 
an  eighty-mesh  sieve,  the  finest  dust  was  washed  away  by 
means  of  water  and  the  separation  carried  on  as  usual,  re- 
peating it  several  times  so  as  to  remove  the  last  traces  of 
thomsenolite.  Finally,  the  purest  powder  was  floated  on  a 
solution  whose  specific  gravity  was  2.611,  a  few  heavier 
particles  were  removed  and  the  solution  diluted  to  the  spe- 
cific gravity  2.551,  when  all  but  a  trace  of  the  powder  sank 
to  the  bottom.  This  material,  amounting  to  over  twelve 
grams,  showed  no  impurity  of  double  refracting  thomseno- 
lite when  examined  under  the  polarizing  microscope,  and  was 
used  in  making  the  following  analysis. 

A  few  remarks  are  necessary  regarding  the  method  of 
analysis.  It  was  found  to  be  practically  impossible  to  decom- 
pose the  mineral  completely  with  sulphuric  acid;  a  residue 
was  always  left  which  could  not  be  dissolved  by  further 
treatment  with  sulphuric  acid,  nor  with  hydrochloric  or  nitric 


CHEMICAL   COMPOSITION  OF  RALSTONITE.        145 

acids.  For  the  determination  of  the  metals  the  mineral  was 
fused  with  sodium  carbonate,  the  fusion  soaked  out  with 
water,  sulphuric  acid  was  added,  and  the  solution  evaporated 
and  ignited  till  the  hydrofluoric  and  excess  of  sulphuric  acids 
were  expelled.  The  mass  was  then  dissolved  in  water  and 
the  metals  determined  according  to  the  usual  methods. 
Sodium  was  determined  once  by  Smith's  fusion  method,  and 
again  by  decomposing  the  mineral  as  far  as  possible  with 
sulphuric  acid,  assuming  that  the  sodium  was  all  in  solution 
and  the  insoluble  portion  some  compound  of  aluminum. 
Water  was  determined  by  igniting  the  mineral  in  a  combus- 
tion tube,  passing  the  vapor  over  dry  sodium  carbonate  and 
collecting  it  in  a  weighed  chloride  of  calcium  tube.  The 
fluorine  could  not  be  determined  by  driving  off  the  silicon 
fluoride.  About  twenty-five  per  cent  of  fluorine  was  readily 
driven  off;  by  continuing  the  decomposition  with  the  tem- 
perature of  the  sulphuric  acid  about  160°,  silicon  fluoride 
was  slowly,  but  in  the  course  of  six  or  eight  hours  never 
completely  given  off.  The  greatest  amount  of  fluorine  which 
we  were  able  to  drive  over  by  this  method  was  about  thirty- 
one  per  cent.  This  is  not  at  all  in  accordance  with  the 
statement  of  Brandl,*  who  states  that  the  decomposition 
commences  at  145°  and  is  completed  at  160°.  We  found  it 
impossible  to  make  a  determination  according  to  the  method 
described  by  him.  Our  determinations  are  made  according 
to  the  Berzelius  method  by  fusing  with  mixed  potassium  and 
sodium  carbonates  and  silica.  They  are  probably  too  low  by 
about  one-half  to  one  per  cent,  judging  from  test  experiments 
which  we  made  on  cryolite.  Our  determinations  are  as  follows : 


Mean. 

Ratio. 

Mg 

4.46 

4.31 

4.39 

0.183  ) 

Na 

4.25 

4.27 

4.26  -f-  46 

0.093  >  0.278 

1.00 

K 

0.12 

0.12 

0.12  -=-  78 

0.002  ) 

Ca 

0.03 

. 

0.03 

Al 

24.23 

24.27 

24.25 

0.882 

3.17 

F 

39.76 

40.05 

39.91 

2.101 

7.56 

H20 

18.72 

18.74 

18.73 

91.69 

*  Loc.  cit. 
10 


146        CHEMICAL   COMPOSITION  OF  RALSTONITE. 

The  ratio  of  (Mg,Na2,K2)  :  Al  =  1  :  3  nearly.  This  ratio 
being  assumed  as  correct,  the  ratio  of  the  fluorine  necessary 
to  unite  with  the  metals  should  be  11,  whereas  we  only 
find  7.56.  The  fluorine  is  therefore  not  sufficient  to  unite 
with  the  metals,  and  this  is  fully  in  accordance  with  the 
suggestion  of  Nordenskiold.  If  the  metals  in  our  analysis, 
which  are  in  excess  of  the  fluorine,  are  united  to  hydroxyl, 
which,  as  has  been  shown  to  be  the  case  in  several  instances, 
is  capable  of  replacing  fluorine,  it  would  be  necessary  to  have 
16.27  per  cent  of  hydroxyl,  corresponding  to  8.61  per  cent  of 
water,  in  order  to  make  the  ratio  (Mg,  Na2,  K2)  :  Al  :  (F  +  OH) 
=  1  :  3  :  11  ;  the  remaining  10.12  per  cent  of  water  would 
then  be  regarded  as  water  of  crystallization,  and  would  corre- 
spond to  two  molecules,  making  the  formula  of  the  mineral 
(Mg,  Na2)Al3(F,OH)n  .  2  H2O.  Making  this  disposition  of 
the  water,  our  analysis  would  be  : 

Ratio. 

Mg  4.39  0.183  ) 

Na  4.27  -f-  46  =  0.093  C  0.278  1.00 

K  0.124-78  =  0.002) 

Ca  0.03 

Al  24.25  0.882  3.17 

P  39.91  2-10 


1100 
OH  16.27  0.957  j 

H20  10.12  0.562  2.02 

99.36 

It  will  be  seen  that  the  assumption  that  hydroxyl  replaces 
fluorine  not  only  makes  up  for  the  deficiency  in  the  analysis 
but  also  leads  to  a  very  satisfactory  ratio.  This  assumption 
is  also  well  supported  by  actual  experiment.  When  the  min- 
eral is  cautiously  heated  in  a  closed  glass  tube,  at  first  neutral 
water,  by  stronger  ignition  acid  water,  is  driven  off.  The 
first  that  comes  off  is  undoubtedly  water  of  crystallization, 
afterwards  the  hydroxyl  is  decomposed  and  fluorine  comes  off 
in  combination  with  the  hydrogen.  By  heating  the  air-dry 
powder  at  100°  C.  there  is  a  loss  of  only  0.10  per  cent;  by 
heating  in  an  air  bath  to  a  temperature  never  exceeding  250° 


CHEMICAL   COMPOSITION  OF  RALSTONITE.        147 

C.  the  mineral  lost  10.37  per  cent,  the  water  going  out  very 
slowly;  the  experiment  was  carried  on  for  over  a  week, 
during  the  last  three  days  of  which  the  weight  remained  very 
constant.  If  this  10.37  per  cent  is  regarded  as  water  of 
crystallization,  the  remaining  8.36  per  cent  would  correspond 
to  15.78  per  cent  of  hydroxyl,  which  agrees  closely  with  the 
figures  in  our  recalculated  analysis.  The  ratio  of  Mg  :  Na2  is 
almost  exactly  2:1,  there  seems  to  be  no  simple  ratio  between 
F  and  OH.  The  excess  of  the  aluminum  in  the  analysis 
may  be  owing  to  some  slight  impurity.  We  have  never  seen 
perfectly  transparent  glassy  crystals  of  ralstonite,  and  their 
turbidity  may  be  owing  to  some  slight  decomposition ;  if 
this  is  the  case  the  alkalies  would  naturally  be  most  readily 
removed,  causing  the  aluminum  to  be  too  high.  If  our 
fluorine  determination  should  be  as  much  as  one  per  cent  too 
low,  which  is  probably  not  the  case,  our  results  would  not 
be  materially  changed.  Using  the  actual  water  of  crystal- 
lization and  hydroxyl  determinations  and  determining  the 
fluorine  by  difference,  we  would  have  for  the  latter  part  of 
our  analysis: 

Ratio. 

F  40.79        2.147  |  q          . 

OH  15.78        0.928  l3'075^278 

H20          10.37  0.576 -f- 278          2.07 

Probably  this  determination  of  fluorine,  by  difference  40.79  per 
cent,  represents  the  true  amount  of  that  element  more  closely 
than  the  results  of  our  actual  determinations. 

Assuming,  as  it  seems  fair  to  do,  that  our  results  and 
conclusions  are  correct  and  that  the  formula  which  we  have 
proposed  is  the  true  one,  namely,  that  the  mineral  is  an 
isomorphous  mixture  of  (Mg,Na2)Al3Fn  .  2H2O  and  (Mg,Na2) 
Al3(OH)n .  2H2O,  in  which  formulae  fluorine  and  hydroxyl 
play  the  same  part  or  are  isomorphous,  let  us  see  if  we  can 
in  any  way  account  for  the  variations  in  the  previously  pub- 
lished analyses,  especially  between  Brandl's  and  our  own,  the 
only  two  complete  analyses.  First,  we  would  emphasize  that 
the  greatest  care  was  used  in  preparing  the  material  for  our 


148        CHEMICAL   COMPOSITION  OF  RALSTONITE. 

analysis ;  the  extremes  in  the  specific  gravity  of  the  powder 
which  we  separated  were  2.611  and  2.551,  or  a  variation 
between  the  lightest  and  heaviest  of  only  0.060.  Second,  our 
analysis  shows  that  our  material  is  practically  free  from 
calcium,  indicating  a  very  complete  separation  from  thom- 
senolite  with  which  the  ralstonite  is  so  intimately  associated, 
and  showing  that  calcium  is  not  an  essential  constituent  of 
the  mineral.  Third,  we  were  not  limited  regarding  the  amount 
of  material  which  we  could  use,  as  we  had  an  abundant  supply 
of  the  pure  mineral.  From  the  same  specimen  from  which 
our  material  was  derived,  one  of  us  by  very  careful  picking 
was  able  to  obtain  nearly  one  gram  of  octahedral  crystals, 
which  were  supposed  to  be  pure,  but  which,  as  is  shown  in 
the  analysis  near  the  beginning  of  this  article,  contained  1.67 
per  cent  of  calcium.  This  indicates  that  a  most  careful  and 
laborious  hand-picking  had  not  been  sufficient  to  free  the 
small  crystals  wholly  from  thomsenolite  from  which  the  cal- 
cium was  unquestionably  derived.  It  seems  highly  probable 
that  other  investigators  have  worked  with  material  containing 
slight  quantities  of  thomsenolite.  Groth,*  for  instance,  states 
that  the  material  which  he  furnished  to  Brandl  for  analysis 
showed  under  the  polarizing  microscope  particles  of  a  strongly 
double  refracting  mineral  with  quadratic  habit  which  was 
unquestionably  thomsenolite.  If  we  assume  that  the  mineral 
is  free  from  calcium,  as  our  analysis  indicates,  and  that  the 
calcium  in  the  other  analyses  is  all  derived  from  thomsenolite, 
we  should  find  by  calculation  the  following  figures  (see  p.  149), 
giving  the  per  cent  of  thomsenolite  in  the  analyzed  material 
and  of  the  mineral  free  from  thomsenolite. 

In  these  analyses  the  ratio  (Mg  +  Na2)  :  Al  =  1  :  3,  very 
nearly,  especially  considering  the  small  quantity  of  mineral 
which  was  used  in  making  the  analyses.  In  Brandl's  analysis, 
the  only  complete  one,  the  fluorine  is  just  sufficient  to  satisfy 
the  metals,  while  the  ratio  (Mg  +  Na2)  :  Al :  F  :  H2O  =  0.97  : 
3 :  10.88  :  2.02,  or  nearly  1  :  3  :  11  :  2,  the  same  as  required 
by  the  formula  proposed  by  us.  In  this  case,  however,  the 

*  Zeitschr.  Kryst,  vii,  474. 


CHEMICAL   COMPOSITION  OF  RALSTONITE.        149 


Nordenskiold. 

Penfield. 

T>        ,-,            vyaicuiatea  lor 
Brandl-(Mg,Na2,)Al3Fu.2H80. 

Thomsenolite 

11.07 

9.28 

8.51 

.  .  . 

Mg 

6.20 

4.29 

3.90 

4.46 

Na 

3.95 

4.27 

5.05 

4.27 

Al 

24.27 

21.19 

23.06 

22.99 

F 

.  .  . 

'.  .  • 

57.68 

58.25 

H20 

15.68 

19.46 

10.17 

10.03 

99.85 

100.00 

Eatio  of      ) 
(Mg,Na2)  :  Al  p 

1.17  :  3 

1.06  :  3 

0.97  :  3 

material  is  a  pure  fluorine  compound,  containing  no  hydroxyl. 
Following  Brandl's  analysis  we  have  given  the  percentage 
composition  calculated  from  the  above  ratio  in  which  the 
Mg  :  Na  =  1:1.  It  will  be  noticed  how  closely  the  figures 
agree  with  the  analysis  of  Brandl. 

The  great  difference  in  the  proportion  in  which  the  metals  are 
united  (Mg  +  Na2)  :  Al  =  1 :  3  in  ralstonite  and  Ca  :  Na  :  Al  = 
1  :  1  :  1  in  thomsenolite,  would  account  for  the  decided  change 
in  the  formula  derived  from  an  analysis  of  a  mixture  of  ralstonite 
with  a  little  thomsenolite.  Brandl's  formula,  3(Na2,Mg,Ca)F2 . 
8A1F8 .  6H2O,  is  therefore  a  little  too  low  in  A1F3.  The  differ- 
ence in  the  deportment  of  the  mineral  when  treated  with  strong 
sulphuric  acid  may  be  owing  to  the  fact  that,  although  the 
fluorine  compound  is  readily  decomposed  by  that  acid  so  that 
Brandl  was  able  to  determine  the  fluorine  by  driving  over  SiF4, 
the  hydroxyl  compound  in  our  mineral  in  some  way  hinders 
the  decomposition  of  the  fluorine  compound,  perhaps  by  being 
in  itself  with  difficulty  decomposed,  and  inclosing  and  thus 
protecting  some  of  the  molecules  of  the  fluorine  compound 
from  decomposition. 

In  thin  sections  under  the  microscope  all  of  the  ralstonite 
appears  very  transparent  and  free  from  visible  inclusions  and 
decomposition  products.  Some  of  the  crystals  on  the  original 
specimen  were  colored  yellow,  and  where  one  of  these  had  been 
cut  through,  the  yellow  substance  was  seen  to  consist  of  a  very- 
thin  film,  probably  of  iron  oxide,  coating  the  crystal.  The 
larger  crystals  were  zonal  in  structure,  the  zones  lying  parallel 


150        CHEMICAL   COMPOSITION  OF  RALSTONITE. 

to  the  faces  of  the  octahedron.  This  zonal  structure  is  scarcely 
perceptible  in  ordinary  light,  being  indicated  by  faint  grayish 
streaks  running  parallel  to  the  contours  of  the  cross  section, 
which  could  not  be  resolved  by  the  use  of  high  powers  into 
visible  inclusions.  In  polarized  light  the  zonal  structure  was 
more  perceptible ;  all  of  the  crystals  show  slight  double  refrac- 
tion and  a  division  of  the  cross  sections  into  fields  reminding 
one  of  the  double  refraction  of  analcite.  The  slightly  double 
refracting  ralstonite  with  its  absence  of  cleavage  is  in  marked 
contrast  to  the  strongly  double  refracting  thomsenolite,  showing 
brilliant  polarization  colors,  blue  of  the  second  order,  distinct 
cleavage  and  inclined  extinction. 

In  closing  we  wish  to  express  our  thanks  to  Professor 
Brush  for  his  liberality  in  providing  us  with  the  rare  material 
for  carrying  on  this  investigation. 


SPERRYLITE,  A  NEW   MINERAL. 

BY  HORACE  L.   WELLS. 
(From  Amer.  Jour.  Sci.,  1889,  vol.  37,  pp.  67-70.) 

A  SMALL  quantity  of  the  remarkable  mineral  which  is  the 
subject  of  this  article  was  sent  to  the  writer  in  October  of  the 
present  year  by  Mr.  Francis  L.  Sperry  of  Sudbury,  Ontario, 
Canada,  chemist  to  the  Canadian  Copper  Co.  of  that  place.  A 
few  tests  sufficed  to  show  that  it  was  essentially  an  arsenide  of 
platinum  and  consequently  of  great  interest,  since  platinum 
has  not  been  found  before,  at  least  as  an  important  constituent, 
in  any  minerals  except  the  alloys  with  the  other  metals  of  the 
platinum  group. 

Since  the  time  mentioned,  Mr.  Sperry  has  furnished,  with 
great  liberality,  an  abundance  of  the  material  for  investigation, 
and  has  given  the  following  account  of  its  occurrence : 

"  The  mineral  was  found  at  the  Vermillion  Mine  in  the  Dis- 
trict of  Algoma,  Province  of  Ontario,  Canada,  a  place  22  miles 
west  of  Sudbury  and  24  miles  north  of  Georgian  Bay,  on  the 
line  of  the  Algoma  Branch  of  the  Canadian  Pacific  Railway. 
The  mine  was  discovered  in  October,  1887,  and  a  3  stamp  mill 
was  put  up  for  the  purpose  of  stamping  gold  quartz.  Asso- 
ciated with  this  gold  ore  are  considerable  quantities  of  pyrite, 
chalcopyrite,  and  pyrrhotite,  and,  at  the  contact  of  ore  and  rock 
and  occupying  small  pockets  in  decomposed  masses  of  the  ore, 
there  is  a  quantity  of  loose  material  composed  of  gravel,  con- 
taining particles  of  copper  and  iron  pyrites.  It  was  in  milling 
this  loose  material  that  several  ounces  of  the  arsenide  of 
platinum  were  gathered  on  the  carpet  connected  with  the 
stamp-mill.  Through  the  kindness  of  Mr.  Charlton,  the 
genial  President  of  the  Vermillion  Mining  Co.,  all  of  the 


152  SPERRYLITE,  A   NEW  MINERAL. 

mineral  that  was  available  was  generously  placed  at  my 
disposal." 

It  may  be  mentioned  here  that  Mr.  Sperry  sent  me,  a  few 
weeks  before  sending  the  arsenide,  a  minute  bead  which  he 
had  obtained  in  making  a  fire-assay  for  gold  on  an  ore,  con- 
sisting chiefly  of  chalcopyrite  and  pyrrhotite,  which  came  from 
the  same  mine  where  the  arsenide  was  found,  but  which  was 
not  the  material  in  which  it  actually  occurred.  This  bead  on 
examination  proved  to  be  composed  largely  of  metals  of  the 
platinum  group,  and,  from  the  color  of  the  precipitate  pro- 
duced by  ammonium  chloride,  it  was  thought  that  it  contained 
a  large  proportion  of  indium,  but  its  small  size  prevented  a 
satisfactory  examination.  With  this  bead  in  mind,  I  expected 
that  the  new  mineral  would  contain  a  considerable  amount  at 
least  of  iridium,  but,  strangely  enough,  none  of  this  metal  was 
found  in  it.  The  material  as  received  consisted  of  a  heavy, 
brilliant  sand  composed  largely  of  the  arsenide ;  but  intermixed 
with  this  a  considerable  amount  of  fragments  of  chalcopyrite, 
pyrrhotite  and  some  silicates  could  be  seen.  In  order  to  purify 
the  substance  it  was  treated  for  a  short  time  with  warm  aqua 
regia  to  remove  sulphides,  etc. ;  then  it  was  treated  for  a  long 
time  with  hot  hydrofluoric  acid  to  remove  the  silicates.  After 
these  treatments  the  sand  possessed  great  brilliancy,  but  it  was 
found  by  microscopic  examination  to  contain  some  transparent 
grains  which  on  chemical  examination  proved  to  be  stannic 
oxide.  Prof.  S.  L.  Penfield  kindly  examined  these  grains  and 
found  that  they  corresponded  perfectly  in  their  optical  properties 
with  cassiterite. 

Nearly  all  the  grains  of  the  new  mineral  showed  extremely 
brilliant  crystal  faces,  though  most  of  the  crystals  were 
fragmentary ;  in  size  they  were  mostly  between  0.05  and 
0.5  mm.  (^  and  -fa  inch)  in  diameter. 

The  color  of  the  mineral  is  nearly  tin  white  or  about  the 
same  as  that  of  metallic  platinum ;  the  fine  powder  is  black. 

The  specific  gravity  taken  twice  on  the  same  8  grams  of 
material,  was  10.420  and  10.424  at  20°  ;  this  material  was  the 
same  that  was  used  for  analysis,  and,  correcting  the  average 


SPERRYLITE,  A   NEW  MINERAL.  153 

of  these  results  for  4.62  per  cent  of  cassiterite,  the  true  specific 
gravity  becomes  10.602. 

The  sand  is  not  easily  wet  by  water  and  shows  a  marked 
tendency  to  float  when  brought  to  its  surface.  By  placing  a 
shallow  layer  of  water  upon  the  mineral  in  a  vessel  it  is  easy 
to  nearly  cover  the  surface  of  the  water  with  a  continuous 
layer  of  the  crystals  by  inclining  the  vessel  repeatedly  so  that 
they  are  brought  to  the  surface.  This  phenomenon  is  not  due 
to  any  oily  substance  upon  the  particles,  for  they  float  with 
equal  readiness  after  being  boiled  with  a  strong  solution  of 
potash  and  washed  with  alcohol  and  ether.  When  they  are 
floating  upon  water  it  is  quite  difficult  to  cause  them  to  sink, 
and  when  carried  to  the  bottom  by  a  stream  of  water  they 
frequently  carry  down  small  bubbles  of  air  which  they 
completely  surround  and  hold  down  by  their  weight.  If  ether 
is  poured  upon  water  on  which  they  are  floating,  they  remain 
suspended  between  the  two  liquids,  and,  by  agitation,  can 
frequently  be  made  to  sink  to  the  bottom  in  spherical  clusters 
surrounding  globules  of  ether. 

The  mineral  is  only  slightly  attacked  by  aqua  regia;  even 
when  it  is  very  finely  pulverized  and  the  strongest  aqua  regia 
is  repeatedly  applied  with  the  aid  of  heat  for  several  days,  the 
solution  is  only  partial. 

Pyrognostics.  —  The  mineral  decrepitates  slightly  when 
heated.  In  the  closed  tube  it  remains  unchanged  at  the 
fusing-point  of  glass.  In  the  open  tube  it  gives  very  readily 
a  sublimate  of  arsenic  trioxide  and  does  not  fuse  if  slowly 
roasted,  but  if  rapidly  heated  it  melts  very  easily  after  losing 
a  part  of  the  arsenic.  Perhaps  its  most  characteristic  reaction 
is  the  following :  when  dropped  on  a  red-hot  platinum  foil  it 
instantly  melts,  gives  off  white  fumes  of  arsenic  trioxide 
having  little  or  no  odor,  and  porous  excrescences  are  formed 
on  the  platinum  which  do  not  differ  in  color  from  the 
untouched  foil. 

Chemical  analysis. — The  following  analyses  of  the  mineral 
were  made  after  a  considerable  amount  of  preliminary  work 
had  been  done  on  it,  the  results  of  which  confirm  these  figures. 


154  SPERRYLITE,   A   NEW  MINERAL. 


I. 

II. 

Mean. 

Ratio. 

As 

40.91 

41.05 

40.98  - 

-    75  =  0.546 

Sb 

0.42 

0.59 

0.50- 

-  122  =  0.004 

•  0.550  =  2 

Ft 

62.53 

52.60 

52.57  - 

-  197  =  0.267 

Rh 

0.75 

0.68 

0.72- 

-  104  =  0.007 

0.274  =  1 

Pd 

trace 

trace 

trace 

Fe 

0.08 

0.07 

0.07 

Sn02 

4.69 

4.54 

4.62 

99.38  99.53  99.46 

The  composition  is  consequently  represented  by  the  formula 
PtAs2,  a  small  portion  of  the  platinum  and  arsenic  being 
replaced  respectively  by  rhodium  and  antimony.  In  composi- 
tion this  mineral  appears  to  be  nearer  Wdhler's  laurite  *  than 
any  other  mineral  now  known.  The  form  of  both  is  isometric, f 
but  their  composition  is  apparently  not  quite  analogous  since 
the  formula  of  laurite  is  given  as  RuS2  -f  ^Ri^Os.  It  is 
possible  that  the  latter  formula  is  slightly  incorrect  since 
Wb'hler  used  an  extremely  small  quantity  (0.3145  gram)  for 
his  analysis  and  acknowledged  the  uncertainty  of  his  results. 
It  is  also  to  be  noticed  that  the  composition  of  the  mineral 
corresponds  to  that  of  the  artificial  platinum  arsenide  made  by 
Murray.^  The  writer  has  confirmed  the  composition  of  this 
artificial  arsenide  by  heating  a  known  weight  of  platinum  to 
redness  and  passing  over  it  vapor  of  arsenic  in  a  current  of 
hydrogen.  The  following  are  the  results  of  the  experiments : 


Pt.  taken.  As  absorbed. 


Ratio. 
Pt.    As. 


I  0.3806      0.2922      1  :  2.02 

II  0.5725      0.4354      1  :  2.00 

III  1.0657      0.8112      1  :  2.00 

It  was  noticed  in  these  experiments  that  the  arsenic 
combines  with  the  platinum  with  incandescence  and  the  alloy 
melts  even  below  a  red  heat  after  a  part  of  the  arsenic  has 
been  taken  up.  At  the  end  of  the  operation,  however,  the 
fused  globule  solidifies,  throws  out  peculiar  arborescent  forms 
and  the  PtAs2  remains  as  a  porous  and  very  brittle  mass 

*  Ann.  Ch.  Pharm.,  cxxxix,  116. 

t  See  next  article  for  crystalline  form  of  Sperrylite. 

t  Watt's  Dictionary. 


SPERRYLITE,  A    NEW  MINERAL.  155 

which  is  neither  fused  nor  changed  in  composition  when 
heated  to  bright  redness  in  hydrogen.  In  its  behavior  with 
solvents  and  its  pyrognostic  properties  the  artificial  compound 
agrees  exactly  with  the  natural  mineral. 

Method  of  analysis.  — -  The  amount  of  substance  taken  for 
each  analysis  was  about  1.5  g.  The  pulverized  substance  was 
gradually  heated  in  a  current  of  chlorine  gas  and  the  volatile 
chlorides  were  absorbed  by  water  in  a  receiver.*  This  liquid 
was  made  ammoniacal,  after  adding  a  very  small  quantity  of 
tartaric  acid  to  keep  the  small  amount  of  antimony  in  solution, 
and  the  arsenic  was  determined  as  magnesium  pyroarseniate. 
From  the  filtrate  from  the  ammonium  magnesium  arseniate, 
antimony  and  a  trace  of  platinum  were  precipitated  as  sul- 
phides, the  sulphide  of  antimony  was  dissolved  in  strong 
hydrochloric  acid,  the  sulphide  was  reprecipitated,  filtered  on 
asbestus  and  weighed  after  proper  heating  in  a  current  of 
carbon  dioxide,  while  the  trace  of  platinum  sulphide  was 
ignited  and  the  residue  was  added  to  the  main  part  of  the 
platinum  left  by  treatment  with  chlorine.  This  part  was 
treated,  with  dilute  aqua  regia;  this  left  an  insoluble  residue 
consisting  of  cassiterite  and  a  finely  divided  black  substance 
which  had  been  found  by  previous  qualitative  tests  to  be 
rhodium.  This  residue  was  fused  with  sodium  carbonate  and 
sulphur,  the  insoluble  rhodium  sulphide  formed  was  ignited 
in  air,  then  in  hydrogen  and  weighed,  while  the  tin  was 
determined  as  stannic  oxide  in  the  usual  way.  The  purity  of 
the  rhodium  was  shown  by  its  complete  solubility  in  fused 
potassium  bisulphate,  also  by  finding  that  it  gave  no  sodium 
double  chloride  soluble  in  alcohol  after  ignition  with  sodium 
chloride  at  a  faint  red  heat  in  a  current  of  chlorine.  About 
f  of  the  total  rhodium  was  found  here.  The  purity  of  the 
stannic  oxide  was  shown  by  reducing  it  in  hydrogen  and 
dissolving  the  metal  in  hydrochloric  acid. 

The  solution  in  aqua  regia  containing  platinum  with  a  little 

*  Preliminary  experiments  with  the  artificial  compound,  PtAs2,  had  shown 
that  all  the  arsenic  passes  off  in  this  operation  if  the  heat  is  applied  slowly 
enough  so  that  the  substance  does  not  melt  after  losing  a  part  of  its  arsenic. 


156  SPERRYLITE,  A   NEW  MINERAL. 

rhodium  and  iron  and  a  trace  of  palladium  was  treated  for 
the  platinum  metals  essentially  by  the  method  of  Glaus ;  *  the 
main  variations  being  a  repeated  separation  of  platinum  from 
rhodium  and  the  weighing  of  platinum  as  metal.  A  distinct 
but  extremely  small  precipitate  of  palladium  cyanide  was 
obtained,  but  the  amount  of  palladium  was  too  small  to 
sensibly  affect  the  balance  when  an  attempt  was  made  to 
weigh  it. 

The  name.  —  The  writer  takes  great  pleasure  in  naming  this 
interesting  mineral  after  Mr.  F.  L.  Sperry,  to  whose  efforts 
this  investigation  is  due. 

*  Rose  und  Finkener,  Analytische  Chemie,  6te  Aufl.,  vol.  ii,  p.  236. 


ON  THE  CRYSTALLINE  FORM  OF  SPERRYLITE. 

BY  S.  L.  PENFIELD. 
(From  Amer.  Jour.  Sci.,  1889,  vol.  37,  pp.  71-73.) 

THE  crystalline  form  of  sperrylite  is  isometric ;  pyritohedral. 
Simple  cubes  are  common,  octahedrons  are  exceptional,  while 
the  majority  of  the  crystals,  which  are  usually  fragmentary, 
show  combinations  of  cube  and  octahedron.  The  first  crystal 
which  was  selected  for  measurement  was  a  fragment  show- 
ing the  above  mentioned  combination ;  one  of  its  central 
octahedral  faces  being  imperfect,  the  best  measurements  were 
obtained  from  a  cubic  to  an  adjoining  octahedral  face.  The 
results,  which  are  given  below,  are  very  satisfactory  consid- 
ering the  small  size  of  the  crystals,  and  prove  that  the 
mineral  is  isometric ;  it  may  also  be  said  that  where  the 
reflections  were  sharpest  and  best  the  values  came  nearest  to 
the  theoretical. 

Calculated. 

a  AO  001  A  Til  54°  34'  54°  44' 

a  A  o  001  A  1T1  54°  46'  54°  44' 

a  A  o  100  A  1T1  54°  35'  54°  44° 

aA0100AllT  54°  45'  54°  44' 

aAalOOA001  90°  2'  90° 

At  first  only  the  above  mentioned  forms  were  detected,  but 
on  sifting  off  the  smallest  crystals  and  carefully  looking  over 
the  larger  ones  some  were  detected  which  suggested  pyrite 
forms.  The  chemical  relation  of  the  mineral,  PtAs2,  to  the 
minerals  of  the  pyrite  group  caused  me  to  make  a  very 
careful  search  for  pyritohedral  forms,  which  was  fortunately 
successful.  Cubes  with  replacement  of  the  edges  are  very 
exceptional ;  a  number  of  them  were  found,  however,  and  in 


158  OAT  THE   CRYSTALLINE 

all  cases  the  replacements,  which  were  necessarily  small  and 
frequently  failed  on  some  of  the  edges,  had  the  arrangement 
required  by  the  combination  of  cube  and  pyritohedron.  The 
best  crystal  selected  for  measurement  was  the  top  of  a  cube, 
measuring  0.35  x  0.45  mm.,  in  combination  with  octahedron 
and  two  small  but  well  developed  pyritohedral  faces ;  the  latter 
gave  very  good  reflections.  The  measured  angles  are 

Calculated. 

001  A  102  26°  28'  26°  34' 

001  A  T02  26°  31'  26°  34' 

Another  crystal  which  was  carefully  measured  was  an  irre- 
gular one  measuring  0.35  and  0.55  mm.  in  two  diameters; 
this  was  developed  in  all  directions ;  in  one  zone  the  four  cubic 
and  four  pyritohedral  faces  were  all  present  in  their  proper 
order  and  gave  satisfactory  measurements,  in  a  second  zone 
four  cubic  and  two  pyritohedral  faces  were  found  and  in  the 
third  zone  four  cubic  and  one  truncating  rhombic  dodecahedral 
face  were  detected ;  this  is  the  only  case  in  which  a  dodecahe- 
dral (110)  face  was  found.  In  a  few  cases  the  characteristic 
combination  of  octahedron  and  pyritohedron  was  detected,  but 
the  latter  faces  were  always  very  small.  These  results  are 
most  satisfactory  and  from  the  number  of  crystals  which  have 
been  examined  and  measured,  in  all  of  which  the  pyritohedral 
faces  occur  with  their  proper  order  and  arrangement,  the 
hemihedral  nature  of  the  mineral  cannot  be  doubted.  Some 
of  the  crystals  are  somewhat  rounded  and  probably  other 
isometric  forms  are  present  but  none  of  them  were  determined. 
The  faces  on  the  crystals  are  usually  very  true  and  must 
possess  a  high  polish  to  give  such  satisfactory  measurements. 
It  may  also  be  noted  that  the  cubic  faces  are  not  usually 
striated  parallel  to  their  intersection  with  the  pyritohedron 
as  is  common  in  pyrite,  although  it  was  a  slightly  striated 
cube  which  first  called  attention  to  the  pyritohedral  nature  of 
the  crystals. 

To  sum  up  the  crystallographic  observations,  the  crystals 
usually  show  the  combination  of  cube  (100),  octahedron 


FORM  OF  SPERRYLITE.  159 

(111),  pyritohedron  (210),  and  very  rarely  dodecahedron 
(110).  Taken  in  connection  with  the  chemical  results  the 
mineral  takes  a  place  in  our  classification  in  the  pyrite  group 
where  an  atom  of  a  metal,  usually  Fe,  Co,  or  Ni  is  united  with 
two  atoms  of  either  S,  As,  or  rarely  Sb,  or  an  isomorphous 
mixture  of  them.  As  this  is  the  first  time  that  platinum  has 
been  found  in  combination  in  a  mineral  it  may  be  noted  that 
Fe,  Co,  and  Ni  and  the  metals  of  the  platinum  group  fall  in 
the  same  series  in  Mendelejeff's  periodic  system  of  the 
elements,  which  gives  additional  grounds  for  putting  this 
mineral  in  the  pyrite  group. 

The  hardness  of  the  mineral  is  between  6  and  7,  which  was 
determined  by  placing  selected  crystals  on  a  bright  feldspar 
surface,  pressing  down  on  them  with  a  soft  pine  stick  and 
rubbing  back  and  forth ;  the  sperrylite  repeatedly  cut  into  the 
feldspar  but  could  not  be  made  to  scratch  quartz.  The 
crystals  have  no  distinct  cleavage  but  are  very  brittle  and 
break  with  an  irregular,  probably  conchoidal  fracture. 


RESULTS   OBTAINED  BY  ETCHING  A  SPHERE 

AND  CRYSTALS   OF   QUARTZ  WITH 

HYDROFLUORIC  ACID. 

BY  OTTO  MEYER  AND  SAMUEL  L.  PENFIELD. 
(From  Transactions  of  Connecticut  Academy,  1889,  vol.  8,  pp.  158-165.) 

A  FEW  years  ago  one  of  us*  published  the  results  of  an 
experiment  of  etching  a  sphere  of  calcite  with  acetic  acid  in 
which  the  symmetry  of  a  calcite  crystal  was  brought  out  by 
the  character  of  the  etchings  on  the  sphere,  and  the  final  result 
of  eating  away  the  greater  part  of  the  calcite  was  a  crystalline 
figure  with  rounded  faces,  but  with  a  decided  steep  scaleno- 
hedral  habit  with  truncations  at  the  extremities  of  the  vertical 
axis.  This  suggested  to  us  the  idea  of  trying  similar 
experiments  on  spheres  cut  from  other  crystals.  The 
difficulty,  of  course,  lies  in  obtaining  spheres  of  perfectly  pure 
homogeneous  material;  the  results  furnish,  however,  an 
interesting  and  instructive  means  of  studying  the  symmetry 
of  any  crystalline  substance  and  as  parts  of  the  sphere  are 
parallel  to  all  possible  faces  of  a  crystal,  as  soon  as  the 
relation  of  the  sphere  to  the  axes  of  the  crystal  is  made  out 
the  character  of  the  etchings  in  any  particular  part  of  the 
sphere  will  determine  the  character  of  the  etching  produced 
by  the  solvent  on  any  crystal  face  parallel  to  that  particular 
part  of  the  sphere.  The  ease  with  which  spheres  of  Japanese 
quartz  can  be  obtained  and  the  readiness  with  which  quartz 
yields  in  certain  directions,  to  the  action  of  hydrofluoric  acid, 
made  the  following  experiments  quite  easy,  while  the  results, 
as  will  be  seen,  are  far  more  striking  than  one  would  at  first 
suppose. 

The  results  of  our  experiments  will  be  better  understood  by 
reviewing  some  experiments  made  in  1855  by  F.  Leydoltf  on 

*  Meyer,  Jahrb.  Minn.,  1883,  i,  74. 

t  Sitz-ber.  der  Wiener  Akad.,  1855,  xv,  p.  59. 


.11  aTAJ'i  rv  -' 

lujg%io  SJiujjp  ksbflBrf-Jrign  ji  'to  ?.>rM\i  oii)  no  Ii'jojJlroiq  sr§nir[o^i    .[ 


v<i  Ijjte^-ro  sj-riii/p  fjyLfiB/i-tlyi   £  to  sooitf   oili   no  haouboTq  8^nifIoJ3 


n  inoil  tiro)  oioffqR'jj  lo  trcq  lotuo-r^  oift  YJ:WB  ^nhee  Ito  JlifgQ-r  Jr.nKi   .8 
JuoJfi  lo  j^^'I  «  ^nnnh  iij-jn  ohoirftmh^d  iftiw  (I»3^v;io  s^imp  bohrr^rf 
-jfl  !:  h:-;itT.r/  -)iiJ  'lo  noij09iif)  oili  ni 

;  IjnoJJil  9iU  'io  eoiiirrunJxo  oil} 


EXPLANATION  OF  PLATES. 

PLATE  II. 

1.  Etchings  produced  on  the  faces  of  a  right-handed  quartz  crystal  by 
hydrofluoric  acid. 

2.  Etchings  produced  on  the  faces  of  a  left-handed  quartz  crystal  by 
hydrofluoric  acid. 

3.  Final  result  of  eating  away  the  greater  part  of  a  sphere  (cut  from  a  left- 
handed  quartz  crystal)  with  hydrofluoric  acid  during  a  period  of  about  eight 
weeks.     Seen  in  the  direction  of  the  vertical  axis.    The  angles  of  the  hexagon 
mark  the  extremities  of  the  lateral  axes. 


PLATE  III. 

1  and  2.  Appearance  of  the  etched  sphere  after  being  in  the  acid  about  four 
days.  1.  Seen  in  the  direction  of  the  vertical  axis.  2.  Seen  in  the  direction 
at  right  angles  to  the  vertical  axis  and  a  prism  of  the  first  order. 

3  and  4.  Appearance  of  the  etched  sphere  after  being  in  the  acid  about 
three  weeks.  3.  Seen  as  in  1.  4.  Seen  about  at  right  angles  to  a  prism  of 
the  second  order,  owing  to  a  mistake  in  taking  the  photograph. 

5  and  6.  Appearance  of  the  etched  sphere  after  being  in  the  acid  about 
seven  weeks.  5.  Seen  as  in  1  and  3."  6.  Seen  as  in  2. 


PLATE  II 


E.  BIERSTADT,    N.   Y, 


PLATE  III. 


Negatives  by  J .  M.  Blake,  New  Haven. 


ARTOTYPE,    E.   BIERSTADT.    N.  Y. 


ETCHING  QUARTZ  WITH  HYDROFLUORIC  ACID.       161 

quartz  crystals  in  which  he  showed  that  hydrofluoric  acid  acts 
very  unequally  on  the  different  kinds  of  faces,  so  that  not 
only  the  rights  and  left-handed  character  of  the  crystals,  but 
also  all  the  complexity  of  twinning  may  be  made  to  appear  by 
etching.  The  experiments  were  repeated  by  us  by  placing 
simple  quartz  crystals  from  Herkimer,  N.  Y.,  in  strong 
hydrofluoric  acid  and  leaving  them  till  sufficiently  distinct 
etchings  were  produced.  In  these  experiments,  some  of 
which  were  carried  on  in  cold  and  some  in  hot  acid,  the 
character  of  the  etching  was  in  all  cases  the  same,  and  as 
quartz  is  dissolved  by  the  acid"  very  slowly  it  is  not  probable 
that  slight  changes  in  the  temperature  or  strength  of  the  acid 
would  have  made  any  appreciable  difference.  On  the  ordinary 
quartz  combination  of  prism,  m  (1010),  positive  rhombohedron 
r  (1011),  and  negative  rhombohedron  z  (0111),  the  following 
etchings  are  very  easily  developed:  The  positive  rhombo- 
hedron r  yields  most  readily  to  the  action  of  the  acid,  becoming 
covered  with  elongated  unsymmetrical  depressions  having  a 
horizontal  direction,  the  heaviest  part  being  to  the  right  in  a 
right-handed  crystal,  figure  1,  plate  II,  and  to  the  left  in  a  left- 
handed  crystal,  figure  2,  plate  II.  The  top  and  middle  edges 
of  these  depressions  are  nearly  straight,  the  bottom  slightly 
curved,  the  widest  end  is  terminated  by  a  straight  edge  having 
the  direction  of  the  zonal  edge  between  r  and  the  adjacent  z 
face.  These  etchings  are  distributed  thickly  over  the  r  faces, 
and  although  they  are  not  all  exactly  alike,  their  general 
character  is  well  represented  in  figures  1  and  2.  The  effect 
of  this  action  is  also  to  eat  away  and  replace  all  of  the  edges 
of  the  crystal  toward  which  the  heaviest  ends  of  the  etchings 
are  turned ;  thus  in  a  right-handed  crystal  between  r  and  r 
(1011  and  1101),  r  and  z  (1011  and  0111)  and  r  and  m 
(1011  and  0110)  all  to  the  right,  while  the  corresponding 
edges  to  the  left,  toward  which  the  points  of  the  depressions 
on  r  are  turned,  are  left  perfectly  sharp,  except  of  course  the 
upper  parts  where  r  (1011)  forms  a  short  edge  with  the 
adjacent  r  (Olll)  face  to  the  left.  In  a  left-handed  crystal, 
this  same  phenomena  can  be  observed  only  with  the  corre- 

11 


162  ETCHING  A    SPHERE  AND   CRYSTALS 

spending  edges  eaten  away  to  the  left  instead  of  to  the  right. 
This  replacement  of  the  edges  is  not  shown  in  Figures  1  and  2, 
but  is  shown  in  the  original  figures  of  Leydolt,  who  also 
determined  the  symbols  of  the  faces  replacing  the  different 
edges.  According  to  our  experience  the  replacement  of  the 
edges  appears  more  like  an  accumulation  of  little  facets,  all 
reflecting  the  light  simultaneously,  than  a  replacement  made 
by  a  single  face.  For  a  discussion  of  the  symbols  of  the 
faces  and  the  determination  of  the  twinning  structure  of  quartz 
as  shown  by  the  etchings  we  refer  our  readers  to  the  original 
paper  of  Leydolt.  If  the  crystals  are  left  in  the  acid  for  a 
sufficiently  long  time  the  edges  between  the  rhombohedron 
faces  become  so  far  eaten  away  that  nothing  is  left  of  the 
original  rhombohedron  faces  and  the  prism  is  left  terminated 
by  the  etching  faces  alone,  which  flatten  out  the  crystal' very 
much  in  the  direction  of  the  vertical  axis. 

On  the  negative  rhombohedron  z,  the  etchings  are  of  an 
entirely  different  character,  composed  of  a  system  of  shallow 
depressions  with  curved  contours,  giving  a  sort  of  feather-like 
marking  with  the  direction  of  greatest  action  turned  toward 
the  heaviest  etching  on  the  positive  rhombohedron,  Figures  1 
and  2,  plate  II.* 

The  prismatic  faces  are  much  less  acted  upon  than  the 
rhombohedron  faces,  the  etchings  varying  somewhat  in  char- 
acter but  consisting  essentially  of  four-sided  depressions  with 
long  and  short  vertical  edges  parallel  to  the  edges  of  the 
prism,  one  straight  steep  edge  on  the  side  of  the  positive 

*  According  to  ray  experience,  these  etchings  on  the  rhombohedron  faces 
furnish  one  of  the  best  methods  of  showing  to  a  beginner  in  crystallography 
that  the  six  faces  which  usually  terminate  a  quartz  crystal,  are  not  the  faces 
of  an  hexagonal  pyramid,  and  all  alike,  but  are  those  of  positive  and  nega- 
tive rhombohedrons.  To  prepare  sections  for  showing  this  with  a  microscope, 
crystals  should  be  etched  till  the  markings  are  sufficiently  distinct,  then  by 
cementing  the  crystal,  with  the  etched  face  down,  to  a  glass  plate  with 
Canada  balsam  and  cementing  glass  plates  on  either  side,  the  quartz  can  be 
ground  away  with  emery  till  the  glass  plates  form  a  large  wearing  surface 
and  the  quartz  is  ground  to  just  the  thickness  of  the  glass  plates ;  then  after 
removing  the  slice  of  quartz  and  cleaning  it,  it  can  be  cemented  to  an  object- 
glass  with  the  etched  surface  up  and  is  ready  for  examination  with  the 
microscope.  —  PENFIELD. 


OF  QUARTZ    WITH  HYDROFLUORIC  ACID.         163 

rhombohedron  r  and  parallel  to  the  zonal  edge  between  m  and 
2,  and  a  shorter  slightly  curved  edge  on  the  side  of  the  nega- 
tive rhombohedron  2.  These  etchings  have  definite  relations 
to  the  symmetry  of  the  crystals  and  are  of  reverse  character 
on  right-  and  left-handed  crystals,  Figures  1  and  2,  plate  II. 
On  adjacent  prismatic  faces,  the  longer  or  shorter  vertical 
edges  are  turned  toward  each  other,  and  by  prolonged  etching 
the  alternating  prismatic  edges,  toward  which  the  shorter 
vertical  edges  of  the  etchings  are  directed,  are  slightly  eaten 
away,  while  the  other  prismatic  edges  remain  sharp  and 
perfect. 

From  a  consideration  of  the  above  we  can  now  more  readily 
understand  the  action  of  hydrofluoric  acid  on  a  sphere  cut 
from  a  simple  quartz  crystal.  A  sphere  of  about  2.44  cm. 
diameter  was  purchased  in  New  York,  and  etched  by  placing 
it  in  a  lead  crucible  containing  rather  strong  commercial 
hydrofluoric  acid,  such  as  can  be  bought  in  rubber  bottles 
from  dealers  in  chemicals.  The  exact  strength  of  the  acid 
was  not  determined.  No  special  care  was  taken  to  place  the 
sphere  in  any  particular  position  in  the  acid,  its  position 
being  accidentally  changed  nearly  every  day  when  the  acid 
was  removed.  The  solution  of  the  quartz  going  on  slowly, 
it  may  be  assumed  that  the  acid  had  a  chance  to  act  equally 
on  all  similar  parts  of  the  sphere.  During  the  progress  of  the 
etching,  which  was  carried  on  slowly  in  the  cold,  photographs 
of  the  etched  sphere  were  obtained  at  three  stages,  which 
seemed  well  suited  for  illustration. 

After  leaving  the  sphere  in  the  acid  for  a  few  hours,  the 
etchings  were  distinctly  observed  and  their  arrangement  on 
the  sphere  was  such  that  its  crystalline  nature  and  relation  to 
hexagonal  axes  could  be  determined.  The  location  of  the 
extremities  of  the  vertical  axis  was  marked  by  the  centers  of 
two  triangular  patches  on  opposite  sides  of  the  sphere,  while 
the  character  and  arrangement  of  the  prominent  etchings  on 
the  positive  rhombohedron  indicated  the  left-handed  charac- 
ter of  the  crystal  from  which  the  sphere  was  cut,  as  well  as 
the  location  of  the  extremities  of  the  lateral  axes.  After 


164  ETCHING  A    SPHERE  AND   CRYSTALS 

being  in  the  acid  for  about  four  days  some  of  the  etchings 
were  very  prominent,  and  the  sphere  had  the  appearance  repre- 
sented in  Figures  1  and  2,  Plate  III.  In  Figure  1  we  are  look- 
ing down  upon  the  sphere  in  the  direction  of  the  vertical  axis. 
In  the  centre  there  is  a  distinct,  somewhat  hexagonal  field,  the 
center  of  which  marks  the  extremity  of  the  vertical  axis. 
This  whole  portion  is  one  where  the  etching  has  gone  on  very 
vigorously,  and  with  the  microscope  it  may  be  seen  that  the 
surface  is  composed  of  minute  triangular  pyramids  grouped 
closely  together.  About  this,  three  prominent  parts,  which 
are  arranged  in  the  alternating  sections  of  the  hexagon,  indi- 
cate the  position  of  the  positive  rhombohedron  by  the  greater 
extent  of  the  etching,  leaving  very  distinct  prominences  with 
their  steep  sides  turned  to  the  right.  A  distinct  ridge  or 
marking,  from  which  the  lines  of  etching  go  off  very  dis- 
tinctly, can  also  be  seen  about  in  the  center  of  each  negative 
rhombohedron.  In  Figure  2,  we  are  looking  at  the  sphere 
about  at  right  angles  to  a  prismatic  face.  A  little  above  the 
center  of  the  figure  and  trending  to  the  right,  the  prominent 
etchings,  indicating  the  position  of  the  positive  rhombohedron, 
can  be  seen,  while  below  and  to  the  right  they  can  also  be  seen 
in  the  position  of  the  lower  positive  rhombohedron.  On  what 
may  be  called  the  equator  of  the  sphere,  midway  between  the 
above  mentioned  prominent  etchings  on  the  positive  rhombo- 
hedrons  above  and  below,  the  extremity  of  one  of  the  lateral 
axes  may  be  located  a  little  to  the  right  of  the  center  of  the 
figure.  On  much  of  the  surface  near  the  equator  of  the 
sphere,  the  original  polish  has  not  been  destroyed.  The 
vigorous  action  of  the  acid  at  the  extremities  of  the  vertical 
axis  is  plainly  seen  accompanied  already  by  a  slight  flattening 
of  the  sphere. 

After  exposing  the  sphere  again  to  the  action  of  the  acid  for 
about  two  weeks  it  had  the  appearance  represented  in  Figures 
3  and  4,  Plate  III.  In  Figure  8,  where  we  are  looking  down 
upon  the  sphere  in  the  direction  of  the  vertical  axis,  three 
parts  on  the  equator,  located  by  the  right-hand  and  upper 
and  lower  left-hand  angles  of  the  hexagon,  indicate  one  ex- 


OF  QUARTZ    WITH  HYDROFLUORIC  ACID.         165 

tremity  of  each  of  the  three  lateral  axes,  and  from  these  parts 
the  lines  of  etching  run  out  very  beautifully  toward  the  center 
and  the  prominent  marking  on  the  rhombohedron  faces.  In 
Figure  4,  where  we  are  looking  at  right  angles  to  the  vertical 
axis,  besides  the  decided  flattening,  a  rhombic  portion,  about 
in  the  center  of  the  field,  is  conspicuous,  the  center  of  which 
locates  the  extremity  of  one  of  the  lateral  axes.  On  this 
portion  not  only  could  the  original  curved  surface  of  the 
sphere  be  detected  but  also  the  original  polish.  The  acid 
having  had  apparently  no  action  on  this  portion  of  the  sphere, 
while  the  etched  portions  come  up  to  meet  this  with  sharp 
and  distinct  angles.  Owing  to  a  slight  misunderstanding,  a 
mistake  was  made  in  photographing  Figure  4,  which  was  not 
discovered  till  it  was  too  late  to  correct  it.  If  we  imagine 
the  sphere  turned  90°  so  that  the  unattacked  portion  would 
appear  at  the  right  and  seen  at  a  tangent,  while  one  of  the 
two  similar  portions  which  are  now  behind  and  out  of  sight 
would  appear  in  the  front  and  a  little  to  the  left,  the  quartz 
would  appear  in  just  the  right  position  to  compare  with 
Figures  2  and  6.  As  it  is,  we  are  looking  at  the  crystal  not 
at  right  angles  to  a  prism  m  but  at  right  angles  to  a  prism 
of  the  second  order  (T2TO). 

By  exposing  the  quartz  for  about  one  month  longer  to  the 
action  of  the  acid  it  appeared  as  represented  in  Figures  5 
and  6,  Plate  III.  In  Figure  5,  which  is  again  a  vertical  view, 
we  can  readily  locate  the  extremities  of  the  three  lateral 
axes  by  the  right-hand  and  upper  and  lower  left-hand  angles 
of  the  hexagon.  At  these  parts  the  curved  contour  of  the 
sphere  is  preserved  for  a  short  distance,  but  between  them 
there  is  a  decided  tendency  toward  a  triangular  cross  section. 
The  sphere,  as  will  be  seen  from  Figure  6,  has  become  ex- 
tremely flattened,  and  the  upper  and  lower  portions  meet 
along  a  sharply  defined  line.  The  etchings  seem  to  arrange 
themselves  along  parallel  lines  or  ridges,  and  some  idea  of 
their  beautiful  arrangement  can  be  obtained  from  the  larger 
reproduction  shown  in  Figure  3,  Plate  II.  In  Figure  6  we 
notice,  in  addition  to  the  extreme  flattening,  two  of  the  three 


166  ETCHING  A    SPHERE  AND   CRYSTALS 

portions  where  the  acid  has  had  very  little  action,  one  taken 
at  a  tangent  to  the  right,  the  other  a  little  to  the  left  of  the 
center ;  these  appear  as  very  conspicuous  parallelograms  ;  they 
have  a  curved  surface  similar  to  that  of  the  original  sphere, 
and  although  the  original  polish  has  disappeared  from  them 
only  the  finest  etchings  can  be  detected  with  the  microscope.  It 
can  almost  be  said  that  the  acid  has  had  no  action  on  these 
three  surfaces,  at  least  not  enough  to  destroy  the  original 
polish  of  the  sphere  till  toward  the  very  end  of  the  experiment, 
and  not  enough  to  appreciably  diminish  the  diameter  of  the 
sphere.  Although  the  original  diameter  was  not  accurately 
measured,  care  was  taken,  soon  after  commencing  the  etching, 
to  cut  a  hole  in  a  cardboard  just  large  enough  to  allow  the 
sphere  to  pass,  and  at  the  conclusion  of  the  etching  the  quartz 
just  touched  at  these  three  points  when  passed  through  the 
same  hole. 

The  quartz  was  still  further  exposed  to  the  action  of  the 
acid  for  about  a  week,  but  the  general  effect  was  not  different 
from  that  shown  in  Figures  5  and  6.  Of  course  the  sphere 
was  further  flattened  in  the  direction  of  the  vertical  axis  and 
the  three  parts  at  the  extremities  of  the  lateral  axes,  where 
the  acid  had  acted  least,  became  considerably  changed,  being 
flattened  out  more  in  a  vertical  direction,  and  therefore  ap- 
pearing as  parallelograms,  relatively  much  more  elongated 
horizontally.  Figure  3,  Plate  II,  is  from  a  photograph  taken 
at  this  stage,  in  which  the  relation  of  these  parts  to  the  longer 
sharp  edge  between  them  is  less  than  in  Figure  5,  Plate  III. 
At  this  stage  the  etching  of  the  sphere  was  stopped  and  the 
specimen  deposited  in  the  collection  of  Prof.  George  J.  Brush, 
New  Haven,  Conn. 

In  review  it  will  be  noticed,  as  is  the  case  in  all  etching,  that 
the  acid  acts  very  unequally  on  different  faces  of  a  crystal  and 
therefore  on  different  parts  of  the  sphere ;  equally,  however, 
on  those  similar  parts  of  the  sphere  which  are  similarly  situated 
with  reference  to  hexagonal  axes.  The  action  is  greatest  at 
the  two  extremities  of  the  vertical  axis.  The  action  seems  to 
be  to  lift  off  or  dissolve  away  layers  of  molecules  from  above  and 


OF  QUARTZ    WITH  HYDROFLUORIC  ACID.         167 

below  while  there  are  three  parts,  each  corresponding  to  one 
of  the  ends  of  the  three  lateral  axes,  where  the  acid  exerts 
practically  no  solvent  action.  These  parts  diminish  in  size  as 
the  action  of  the  acid  continues,  but  not  by  any  action  of  the 
acid  upon  them  directly,  except  as  the  molecules  were  taken 
away  from  above,  below,  and  at  the  sides.  This  is  one  of  the 
most  striking  features  of  the  experiment  that  in  these  three 
directions  quartz  is  almost  absolutely  insoluble  in  hydrofluoric 
acid.  As  a  study  in  symmetry,  the  experiment  all  along 
was  a  very  interesting  one.  The  etched  sphere  could  never 
be  divided  by  a  plane  into  symmetrical  halves  and  showed 
throughout  all  of  the  experiment  the  trapezohedral  character 
of  a  quartz  crystal.  The  sphere  was  cut  from  a  crystal  which 
would  have  shown  etchings  like  those  in  Figure  2,  Plate  II. 
The  accompanying  illustrations  give  only  a  faint  idea  of  the 
beauty  of  the  etched  sphere,  it  being  impossible  to  reproduce 
the  delicacy  and  beauty  of  the  markings  as  they  appeared  on 
the  perfectly  transparent  material  of  the  quartz. 

NOTE.  —  Owing  to  a  mistake  in  interpreting  the  character  of 
the  etching  figures,  it  was  stated  in  the  original  article  that  the 
sphere  was  cut  from  a  right-handed  crystal.  This  error  was 
pointed  out  by  A.  C.  Gill  (Zeit.  Kryst.,  vol.  22,  p.  97).  The 
forms  shown  by  Figure  3,  Plate  II,  and  Figures  1-6,  Plate  III, 
are  the  result  of  etching  a  sphere  cut  from  a  left-handed  quartz 
crystal. — EDITOR. 


ON   SPANGOLITE,   A  NEW   COPPER   MINERAL. 

BY  S.  L.  PENFIELD. 
(From  Amer.  Jour.  Sci.,  1890,  vol.  39,  pp.  370-378.) 

DURING  the  summer  of  1889,  while  visiting  Mr.  Norman 
Spang  of  Etna,  Allegheny  County,  Pa.,  my  attention  was 
called  by  him  to  a  beautifully  crystallized  specimen  of  an 
unknown  mineral  which  he  had  obtained  from  a  man  li ving 
near  Tombstone,  Arizona.  The  original  owner  had  a  small 
collection  of  minerals  which  he  had  gathered  together  within 
a  radius  of  about  two  hundred  miles,  but  he  had  no  idea  of 
just  where  he  had  found  the  specimen,  though  he  thought 
it  was  from  the  Globe  District.  Mr.  Spang  had  forgotten 
the  name  of  the  man  from  whom  he  had  secured  it,  so  that 
until  other  specimens  are  found  uncertainty  must  exist  con- 
cerning the  exact  locality  and  mode  of  occurrence.  On 
expressing  a  desire  to  investigate  the  mineral,  Mr.  Spang  very 
generously  lent  me  the  specimen  and  has  since  presented  me 
with  it.  It  is  now  deposited  in  the  collection  of  Professor 
Brush,  at  New  Haven. 

A  preliminary  blowpipe  examination  showed  that  the  min- 
eral was  undoubtedly  a  new  species  and  essentially  a  hydrated 
sulphate  and  chloride  of  copper,  and  I  take  pleasure  in  not 
only  expressing  at  this  time  my  thanks  to  Mr.  Spang  for  his 
kindness  but  also  in  naming  the  mineral,  which,  as  will  be 
shown,  is  of  unusual  interest,  Spangolite^  after  him. 

The  original  specimen,  which  was  about  the  size  of  a  small 
hen's  egg,  consisted  of  a  rounded  mass  of  impure  limonite 
which  was  mostly  covered  with  hexagonal  crystals  of  spango- 
lite,  associated  with  a  few  crystals  of  azurite  and  some  slender 
prismatic  crystals  of  a  copper  mineral  containing  chlorine, 
probably  atacamite. 


ON  SPANGOLITE.  169 

The  crystallization  of  spangolite  is  hexagonal,  rhombohe- 
dral.  The  habit  of  the  crystals  does  not  vary  much  as  they 
all  show  a  prominent  hexagonal  basal  plane  and  a  series  of 
apparently  holohedral  hexagonal  pyramids,  which,  as  will  be 
shown,  must  be  taken  as  pyramids  of  the  second  order.  Some 
of  the  crystals  have  the  habit  of  Figure  1,  showing  a  prism, 
which  is  always  so  dull  and  striated  that  it  gives  no  reflection 
of  light,  associated  with  pyramids  and  a  basal  plane.  Others 
are  flatter,  Figure  2,  and  show  a  large  series-  of  pyramids 


FIGURE  1.  FIGUBE  2. 

which  oscillate  with  one  another,  giving  rise  to  prominent 
striations  which  run  horizontally  about  the  crystal  and  make 
the  identification  of  the  pyramids  a  difficult  matter.  On  the 
crystals  there  is  occasionally  found  a  prism  of  the  first  order, 
m,  which  is  small  but  gives  good  reflections.  The  material 
which  could  be  used  for  the  investigation  was  limited,  but 
great  care  was  taken  to  select  only  the  best  and  purest 
crystals  for  making  the  crystallographic  and  chemical  inves- 
tigation. A  number  of  small  crystals  were  selected  which 
were  measured  in  the  prominent  pyramidal  zones  between 
the  basal  planes.  The  basal  planes  usually  gave  very  good 
reflections  of  the  signal  but  on  turning  the  crystal  on  the 
goniometer,  after  the  pyramids  came  into  a  position  to  reflect 
light,  there  usually  followed  an  unbroken  band  of  signals 
reflected  from  these  faces,  owing  to  their  striations  and 
oscillatory  combinations.  In  this  band  of  reflections  prom- 
inent parts  could  usually  be  located  which  indicated  the 
position  of  distinct  pyramidal  faces.  On  measuring  fifteen 
independent  pyramidal  zones  on  five  different  crystals,  only 
one  crystal  was  found  which  gave  sharp  reflections  from  the 


170  ON  SPANGOLITE, 

pyramidal  faces;  from  this  an  angle  was  obtained  of  c  A  p, 
0001  A  2112  =  63°  32'.  Still  better  results  were  obtained  on 
measuring  from  pyramid  to  pyramid,  when  the  reflections  of 
the  signal  are  not  so  much  disturbed  by  the  striations  and 
the  value  given  below,  which  will  be  accepted  as  the  funda- 
mental measurement,  was  obtained 

p  A/,  2112  A  1122  =  53°  11'  30" 

From  this  the  length  of  the  vertical  axis,  c  ==  2.0108,  was 
calculated. 

The  largest  of  all  the  crystals  was  fortunately  so  situated 
that  it  could  be  measured  without  detaching  it  from  the 
specimen.  It  was  very  symmetrical  and  had  the  habit  shown 
in  Figure  1 ;  it  measured  about  8  mm.  in  diameter  and  was 
54  mm.  high.  The  forms  observed  on  this  and  other  crystals 
are  as  follows : 

c,     0001  k,   1128  r,    3358  x,    3354 

a,     1120  w,    1126  I,    3357  y,   1121 

m,  T010  0,    1124  p,   1122  z,  3352 

Of  the  foregoing  forms  «,  <?,  and  p  are  prominent  on  all 
crystals,  and  o  and  m  subordinate.  The  tables  of  measured 
and  calculated  angles,  and  the  discussion  of  the  forms  on  the 
more  complex,  striated  crystals,  Figure  2,  are  here  omitted. 

Cleavage.  —  The  cleavage  of  spangolite  is  very  perfect 
parallel  to  the  base;  this  was  a  great  help  in  studying  the 
crystals  as  many  of  the  measurements  were  obtained  from 
cleavage  planes.  Inclined  to  the  base  the  crystals  usually 
broke  with  a  conchoidal  fracture ;  in  only  one  case  a  distinct 
cleavage  was  observed  parallel  to  the  pyramid  p,  the  angle  of 
the  cleavage  measured  on  to  the  base  being  63°  28',  calculated 
63°  33J'.  Thin  plates  of  the  mineral  are  non-elastic  and 
brittle. 

Etching.  —  Experiments  made  by  etching  the  mineral  with 
acids  gave  results  which  add  very  much  to  a  proper  under- 
standing of  the  crystals.  It  is  readily  soluble  in  dilute  mineral 


A   NEW  COPPER  MINERAL. 


171 


acids  and  the  perfect  basal  cleavage  makes  it  easy  to  obtain 
oriented  sections  suitable  for  etching.  The  figures  differed 
both  with  the  character  and  strength  of  the  acid,  but  always 
showed  a  decided  rhombohedral  symmetry.  Figure  3  repre- 
sents the  character  of  some  etchings  produced  by  dilute 
sulphuric  acid.  The  figures  which  are  very  perfect  are  about 
0.066  mm.  in  diameter  and  have  the  shape  of  a  section  across 
a  scalenohedron.  Some  of  the  depressions  are  bounded  below 
by  a  basal  plane,  others  taper  to  a  point,  while  the  scalenohe- 
drons  oscillate  and  give  rise  to  delicate  striations  which  are 
beautifully  brought  out  under  the  microscope  by  a  slight 
change  of  focus.  The  obtuse  angle  of  the  scalenohedron 
section  measured  under  the  microscope  was  about  133°,  from 
which  the  relation  on  the  lateral  axes  a  :  fa  :  fa,  is  calculated. 


FIGURE  3. 


FIGURE  4. 


FIGURE  6. 


This  requires  an  angle  of  133°  10'.  Figure  4  represents  some 
etchings  produced  by  very  dilute  sulphuric  acid :  1  c.  c.  of  con- 
centrated H2SO4  diluted  with  80  c.  c.  of  water.  These  also 
have  a  scalenohedral  cross  section  and  are  about  0.06  mm.  in 
diameter.  The  obtuse  angle  of  the  cross  sections  measures 
about  152°,  from  which  its  relation  on  the  lateral  axes  a:^aika 
was  calculated.  The  required  angle  is  152°  12'.  There  are  also 
some  steep  rhombohedral  depressions,  with  somewhat  curved 
contours  developed  on  this  section.  Some  of  the  etchings 
produced  by  hydrochloric  acid  are  shown  in  Figure  5,  where 
the  hexagon  is  divided  into  three  parts.  The  figures  shown 
in  part  a  represent  deep  hexagonal  depressions  whose  cross 
section  is  that  of  a  pyramid  of  the  second  order ;  these  have 


172  ON  SPANGOLITE, 

a  diameter  of  about  0.035  mm.  and  are  surrounded  above 
with  shallow  and  very  delicate  rhombohedral  depressions 
with  curved  contours.  In  part  b  we  have  again  scalenohedral, 
surrounded  by  shallow  and  more  delicate  rhombohedral, 
depressions.  The  obtuse  angle  of  the  scalenohedral  sections 
measured  129°,  from  which  its  relation  on  the  lateral  axes 
a  :  \a  :  %a  may  be  calculated.  The  required  angle  is  129°  26'. 
In  part  c  we  have  again  represented  simple  scalenohedron 
depressions  which  are  about  0.025  mm.  in  diameter  and  were 
produced  by  a  very  dilute  acid,  1  c.  c.  concentrated  HC1  diluted 
with  160  c.  c.  of  water.  The  obtuse  angle  of  the  scalenohedron 
measured  about  142°,  indicating  a  relation  on  the  lateral  axes 
of  a  :  fa  :  3a.  The  required  angle  is  141°  48'.  With  nitric 
acid  the  figures  are  very  similar  to  those  produced  by  hydro- 
chloric :  in  all  cases  it  was  observed  that  with  very  dilute 
acids  there  was  a  tendency  to  form  scalenohedral,  and  with 
stronger  rhombohedral,  depressions.  When  we  compare  the 
position  of  these  rhombohedral  and  scalenohedral  etchings  to 
the  outer  hexagon,  which  in  Figures  3,  4,  and  5  indicates  the 
outline  of  the  crystal  section,  we  see  at  once  that  the  pyramids 
on  the  mineral  must  be  of  the  second  order.  It  should  be 
stated  here  that  the  etchings  were  of  very  great  beauty  and 
perfection,  the  outline  of  the  scalenohedral  cross  sections  being 
in  almost  all  cases  very  distinct  and  free  from  distortions  of 
any  kind,  so  that  the  angles  could  be  measured  with  com- 
parative accuracy. 

Optical  properties.  —  The  color  of  the  mineral  by  reflected 
light  is  dark  green,  cleavage  plates  by  transmitted  light  are 
light  green.  Prof.  H.  L.  Wells  examined  a  basal  section  of 
the  mineral  0.4  mm.  thick  with  the  spectroscope.  When  the 
slit  was  very  narrow  the  light  transmitted  by  the  mineral  gave 
a  narrow  spectrum  with  a  maximum  of  light  in  the  green 
at  about  X  525.  There  was  a  total  absorption  of  the  red  and 
yellow,  running  well  into  the  yellowish-green.  At  the  other 
end  of  the  spectrum  there  was  a  decided  absorption  of  the 
blue  and  a  total  absorption  of  the  violet.  Pleochroism  is  not 
very  marked.  The  ordinary  ray  is  green  while  the  extra- 


A   NEW  COPPER  MINERAL.  173 

ordinary  is  a  decided  bluish  green.  Cleavage  plates  show 
perfectly  normal  optical  properties.  In  convergent  polarized 
light  they  yield  a  black  cross  surrounded  by  rings  which  are 
bordered  by  green  and  blue.  The  double  refraction  is  quite 
strong  and  negative.  Considerable  difficulty  was  obtained  in 
making  a  prism  from  a  crystal  of  the  mineral  with  its  edge 
at  right  angles  to  the  perfect  basal  cleavage,  but  a  small  one 
was  obtained,  with  an  angle  of  37°  48',  from  which  the  indices 
of  refraction  were  determined.  The  prism  was  opaque  to 
the  red  and  yellow  lights  of  lithia  and  soda  flames,  even  to 
the  yellowish-green  light  of  a  thallium  flame.  With  an 
ordinary  kerosene  flame  the  prism  yielded  two  narrow  green 
spectra,  with  a  minimum  deviation  of  26°  25'  for  the  extra- 
ordinary and  28°  46'  for  the  ordinary  ray.  These  were 
measured  from  the  brightest  part  of  the  spectra,  which,  from 
the  spectroscopic  examination,  had  been  located  at  about 
X  525.  The  two  indices  of  refraction  from  the  values  given 
above  are  co  1.694,  e  1.641. 

Other  physical  properties.  —  The  hardness  of  the  mineral 
on  the  basal  plane  is  about  2,  on  the  pyramidal  faces  nearly  3. 
The  specific  gravity  was  taken  very  carefully  with  a  chemical 
balance  011  the  purest  material,  which  was  selected  for  chemi- 
cal examination.  After  boiling  the  crystals  in  water,  to  expel 
any  air,  three  separate  portions  weighing  respectively  0.2143, 
0.1787,  and  0.1538  grams  gave  3.147,  3.133,  and  3.142,  an 
average  of  3.141  as  the  specific  gravity. 

Chemical  composition.  —  More  than  three  grams  of  excep- 
tionally pure  material  were  readily  obtained  by  sacrificing 
about  one-half  of  the  crystals  on  the  specimen.  As  the  ma- 
terial was  somewhat  limited,  a  method  of  analysis  was  adopted 
by  which  nothing  could  well  escape  detection  and  a  quali- 
tative and  quantitative  analysis  was  carried  on  with  a  single 
sample,  the  results  of  which  are  given  below.  The  fourth 
analysis  was  made  on  an  entirely  different  sample  from  that 
which  yielded  the  figures  in  the  first  three  columns. 

The  analysis  yields  a  ratio  of  SO3  :  Cl  :  A12O8  :  CuO  : 
H2O  =  1.01  :  0.93  :  0.51  :  6.0  :  9.07  or  very  nearly  1  :  1  :  0.5  : 


174  ON  SPANGOLITE, 


I. 

n. 

in. 

IV. 

Average. 

Calculated 
Ratio.            for  CufiAl 

C1S010.9H20 

S08 

.  .  . 

10.08 

10.11 

10.14 

10.11 

0.126 

1.01 

10.03 

Cl 

4.12 

.  .  . 

4.10 

4.11 

4.11 

0.116 

0.93 

4.45 

A1203 

6.59 

.  .  . 

6.51 

6.70 

6.60 

0.064 

0.51 

6.45 

CuO 

59.57 

.  .  . 

59.47 

59.50 

59.51 

0.7495 

6.00 

59.75 

H20 

.  .  . 

20.32 

20.49 

20.41 

1.134 

9.07 

20.32 

100.74 

101.00 

0, 

equivalent  of  Cl 

0.92 

1.00 

99.82  100.00 

6  :  9,  from  which  the  somewhat  complicated  and  remarkable 
formula,  Cu6AlClSO10.  9H2O  is  obtained.  No  doubt  can  how- 
ever exist  concerning  this  formula ;  not  only  was  the  ma- 
terial beautifully  crystallized  and  of  unusual  purity,  but  the 
analyses  of  two  separate  samples  are  identical  within  the 
error  of  analysis  and  the  ratio  is  throughout  very  sharp; 
moreover  the  calculated  composition  agrees  very  well  with 
the  results  of  analysis.  A  slight  deficiency  in  chlorine  may 
result  from  a  partial  replacement  of  that  element  by  hydroxyl, 
which,  if  true,  would  diminish  somewhat  the  slight  excess 
of  water.  The  method  of  analysis  was  as  follows :  A  weighed 
quantity  of  the  mineral  lost  water  slowly  by  standing  in  a 
desiccator  over  sulphuric  acid,  amounting  to  0.30  per  cent 
in  thirty-six  hours,  but  it  regained  almost  all  of  this  loss  by 
standing  uncovered  in  the  air.  Heated  for  an  hour  at  100° 
C.  it  lost  about  0.49  per  cent,  but  also  regained  this  by  stand- 
ing in  the  air.  The  analyses  were  all  made  on  air-dry  powder. 
Water  was  determined  by  heating  the  mineral,  contained  in 
a  platinum  boat,  in  a  hard  glass  tube  provided  with  a  loose 
plug  of  sodium  carbonate  at  one  end,  through  which  the 
water  vapors  were  conducted  before  absorption  in  a  weighed 
chloride  of  calcium  tube.  A  good  deal  of  chloride  of  copper 
distilled  off  from  the  mineral.  In  some  cases  the  contents 
of  the  boat  were  dissolved  in  nitric  acid,  the  tube  cleaned  out 
carefully,  and  a  conjplete  analysis  made  on  one  portion.  A 
new  portion  being  taken,  it  was  dissolved  in  nitric  acid  and 
the  chlorine  precipitated  with  silver  nitrate.  The  weighed 
silver  chloride  when  tested  was  found  to  contain  no  bromine 


A   NEW  COPPER  MINERAL.  175 

or  iodine  and  when  ignited  in  hydrogen  gas  yielded  a  weight 
of  metallic  silver  agreeing  with  the  composition  AgCl.  After 
removing  the  excess  of  the  silver  from  the  solution  with 
hydrochloric  acid  the  SO3  was  precipitated  with  BaCl2,  care 
being  taken  to  avoid  a  loss  owing  to  the  solubility  of  BaSO4 
in  the  aqua  regia  which  was  present  in  the  analysis.  After 
separating  the  excess  of  barium  with  sulphuric  acid  the  solu- 
tion was  evaporated  to  expel  the  nitric  acid,  after  which  the 
copper  was  precipitated  with  hydrogen  sulphide  and  weighed, 
after  ignition  in  hydrogen  gas,  as  Cu2S.  A  portion  of  the 
copper  precipitate  was  carefully  tested  for  other  metals,  but 
none  were  found.  The  filtrate  from  the  copper  sulphide, 
when  evaporated  to  dryness  and  ignited,  left  a  residue  which 
proved  to  be  sulphate  of  alumina ;  this  was  dissolved  in  acid, 
precipitated  in  ammonia  and  weighed  as  A12O3.  A  weighed 
quantity  of  the  oxide  was  carefully  tested  for  beryllium,  but 
none  was  found,  and  after  conversion  into  sulphate  and 
evaporation  with  the  right  quantity  of  K2SO4  it  yielded  alum 
crystals.  The  filtrate  from  the  alumina  yielded  no  percep- 
tible residue  when  evaporated  to  dryness,  proving  that  every- 
thing had  been  separated  from  the  solution. 

Pyrognostic  and  chemical  tests.  —  Before  the  blowpipe  the 
mineral  fuses  at  about  3  to  a  black  slaggy  mass,  coloring  the 
flame  green.  On  charcoal  with  soda  in  reducing  flame  it 
yields  globules  of  metallic  copper.  Heated  in  the  closed  tube 
it  gives  abundant  water  which  has  a  strong  acid  reaction. 
Insoluble  in  water,  but  readily  soluble  in  dilute  acids. 

NOTE.  —  Since  the  publication  of  the  foregoing  paper  spango- 
lite  has  been  identified  by  Professor  H.  A.  Miers  on  two  speci- 
mens from  Cornwall.  (Min.  Mag.,  vol.  10,  p.  273.)  The  crystals 
from  Cornwall  are  hemimorphic  and,  attention  having  been  called 
to  this  fact,  it  may  be  seen  that  the  crystals  on  the  Arizona 
specimen  are  likewise  hemimorphic.  Figure  1,  which  shows 
no  hemimorphic  development,  is  in  reality  a  twin.  The  nature 
of  the  twinning  and  the  pyroelectric  properties  of  the  crystals 
are  yet  to  be  studied.  —  EDITOR. 


ON  MORDENITE. 

BY  LOUIS  V.  PIRSSON. 
(From  Amer.  Jour.  Sci.,  1890,  vol.  40,  pp.  232-237.) 

UNDER  the  name  of  mordenite  in  1864,  How*  published  a 
description  of  a  new  zeolite,  occurring  at  Morden  and  Peter's 
Point,  Nova  Scotia.  To  this  species  he  assigned  the  general 
formula  RO  .  R2O3  .  9SiO2  .  6H2O.  The  correctness  of  this 
formula  has  long  been  considered  doubtful,  owing  to  the  high 
ratio  of  silica  to  the  bases  and  it  is  supposed  that  How  analyzed 
a  mixture  of  some  zeolite  with  silica,  more  especially  as  his 
mineral  did  not  occur  in  distinct  crystals.  It  will  therefore 
be  of  interest  to  announce  the  rediscovery  of  this  interesting 
species  in  a  new  locality,  to  present  a  new  analysis  of  pure 
material,  proving  the  correctness  of  How's  work,  together 
with  a  discussion  of  its  composition  and  a  description  of  its 
crystal  form  and  other  physical  properties. 

The  material  upon  which  the  present  work  is  based  I 
collected  in  October,  1889,  while  engaged  in  temporary  field 
work  on  the  Yellowstone  Park  division  of  the  U.  S.  Geological 
Survey,  in  western  Wyoming.  The  locality  was  one  of  the 
high  points  of  the  ridge  running  eastwardly  from  Hoodoo 
Mountain,  and  forming  part  of  the  divide  between  branches  of 
Crandall  Creek  whose  waters  run  into  Clark's  Fork  and  the 
head  of  the  Lamar  River  or  east  fork  of  the  Yellowstone. 
The  locality  is  several  miles  from  Hoodoo  Mountain.  The 
mordenite  occurs  lining  the  amygdaloidal  cavities  of  a  mass  of 
decomposed  basalt,  one  of  the  former  inclusions  in  the  basic 
breccia  forming  the  ridge.  At  the  time  it  was  unfortunately 
supposed  to  be  one  of  the  commonly  occurring  zeolites  and 

*  Jour,  of  the  Chemical  Soc.,  II,  ii,  p.  100,  1864. 


ON  MORDENITE.  177 

only  a  small  specimen  was  secured.  Recently,  while  examin- 
ing some  material  obtained  in  that  region,  this  specimen  came 
to  light  and  as  some  tests  failed  to  classify  it,  a  complete 
investigation  was  undertaken,  with  the  results  here  presented. 
In  order  to  obtain  enough  material  for  analysis  nearly  the 
whole  of  the  specimen  had  to  be  sacrificed.  As  the  mordenite 
occurs  in  very  small  crystals,  one  of  average  size  measuring 
under  the  microscope  1  mm.  in  height  and  breadth  by  about 
0.4  mm.  in  thickness,  it  would  have  been  impossible  to  pick 
out  sufficient  pure  material  for  analysis. 

A  preliminary  specific  gravity  determination  showed  it  to 
be  about  2.14  and  it  was  therefore  determined  to  separate  it 
by  means  of  the  Thoulet  solution,  it  being  so  much  lighter 
than  the  pyroxene  and  other  minerals  that  might  be  expected 
in  the  basalt.  The  specimen  was  therefore  crushed  fine 
enough  to  pass  through  an  eighty-mesh  sieve,  washed  free 
from  dust  and  twice  separated  by  the  Thoulet  solution.  In  the 
last  operation  the  mordenite  floated  on  a  solution  of  2.179, 
and  sank  when  the  density  was  lowered  to  2.119.  Its  specific 
gravity  is  therefore  between  these  two  determinations.  The 
density  of  the  Thoulet  solution  .was  taken  with  a  Westphal 
balance. 

The  material  thus  obtained  after  washing  and  drying,  proved, 
on  examination  under  the  microscope,  to  be  of  exceptional 
purity,  consisting  wholly  of  crystal  fragments,  showing 
characteristic  outlines  and  cleavage,  and  with  no  adherent 
particles  of  any  foreign  substance.  The  greater  part  were 
perfectly  transparent  and  colorless;  occasional  fragments 
showed  a  very  pale  brownish  discoloration  in  spots,  as  if  due 
to  the  infiltration  and  deposition  of  a  minute  amount  of  iron 
ore  or  organic  matter  into  cleavage  cracks.  In  no  respect  as 
to  appearance  or  their  action  on  polarized  light  did  these 
latter  differ  from  the  colorless  pieces. 

A  test  was  again  made  with  the  Thoulet  solution  to  ascertain 
if  any  difference  in  specific  gravity  could  be  found  between  the 
two.  Very  careful  testing  failed  to  show  any  whatever. 
Both  floated  and  sank  at  precisely  the  same  densities  and  in 

12 


178  ON  MORDENITE. 

precisely  the  same  proportion.  Great  confidence  is  therefore 
felt  in  the  purity  of  the  material  operated  upon.  The  perfect 
separation  by  the  Thoulet  solution  was  no  doubt  due  to  the 
heavy,  crumbly  nature  of  the  basalt  with  which  the  mordenite 
was  associated  and  its  own  brittleness  and  low  specific  gravity. 
By  this  means  about  one  gram  of  the  pure  mineral  was  obtained. 
It  was  thoroughly  washed  and  dried  at  about  70°  F.  It  was 
then  finely  powdered  and  subjected  to  analysis.  A  preliminary 
test  showed  that  the  mineral  was  scarcely  attacked  by  boiling 
hydrochloric  acid.  The  material  was  therefore  divided  into 
two  equal  portions  and  in  the  first,  which  was  brought  into 
solution  by  a  mixture  of  sulphuric  and  hydrofluoric  acids, 
everything  was  determined  except  the  silica.  The  second 
portion  was  subjected  to  a  sodium  carbonate  fusion  and 
everything  determined  save  the  alkalies. 

The  water  was  first  determined  in  both  portions  by  ignition. 
It  was  given  off  easily,  and  the  weight  became  constant  at  a 
moderate  red  heat.  Before  determining  the  water  in  No.  I, 
it  was  found  that  the  powdered  mineral  lost  about  3.6  per 
cent  of  water  by  one  hour's  exposure  to  a  heat  of  100°  C. 
The  process  for  determining  magnesia  and  the  alkalies  was  as 
follows.  After  separating  in  No.  I,  the  alumina  and  ferric 
oxides  by  ammonia  and  the  lime  by  ammonium  oxalate,  the 
filtrate  was  evaporated  and  ignited  gently  in  a  platinum 
dish  until  all  ammonium  salts  were  driven  off.  The  residue 
was  then  dissolved  in  a  little  water,  and  a  roughly  estimated 
amount  of  previously  purified  barium  hydroxide  added.  By 
this  means  all  the  sulphuric  acid  and  magnesia  present  were 
thrown  down  and  the  alkalies  obtained  in  the  filtrate  in  a 
form  suitable  for  conversion  into  chlorides  and  for  deter- 
mination, after  the  excess  of  barium  hydroxide  had  been 
removed  by  ammonium  carbonate.  The  trace  of  magnesia 
was  then  easily  separated  from  the  precipitate  of  barium 
sulphate  by  hydrochloric  acid,  filtered  off  and  determined. 

The  analysis  was  at  all  points  carried  on  both  as  a  qualita- 
tive as  well  as  a  quantitative  one.  It  yielded  the  following 
results : 


ON  MORDENITE. 


179 


ii. 


Mean. 


Ratio. 


Si02 

.  .  . 

66.40 

66.40 

1.106 

1.106 

9.00 

A1203 

11.32 

11.01 

11.17 

0.1084  | 

0.112 

0.91 

Fe203 

0.62 

0.52 

0.57 

0.0036  } 

CaO 

1.89 

1.98 

1.94 

0.0346  ^ 

MgO 
K20 

0.20 
3.58 

0.14 

0.17 
3.58 

0.0042  1 
0.0379  ( 

0.113 

0.92 

Na20 

2.27 

.  .  . 

2.27 

0.0366  J 

H20 

13.31 

13.31 

13.31 

0.7394 

0.7394 

6.01 

Total 

99.41 

From  these  ratios  it  will  be  seen  that  the  mineral  agrees 
closely  with  How's  general  formula  RO  .  A12O3 .  9SiO2 .  6H2O, 
and  if  the  slight  amount  of  magnesia  is  taken  as  replacing  lime 
it  is  evident  that  the  protoxide  bases  are  CaO  :  Na2O  :  K2O  = 
1:1:1.  The  composition  is  then  (JK2O,  JNa2O,  JCaO). 
A12O3  .  9SiO2  .  6H2O.  In  the  type  of  mordenite  analyzed  by 
How  there  was  only  a  slight  trace  of  potash  and  his  com- 
position showed  (JNa2O,  f CaO)  .  A12O3  .  9SiO2 .  6H2O  and 
in  the  present  mineral  one  molecule  of  K2O  replaces  one  of 
CaO  in  How's  type.  The  ratios  show  a  slight  deficiency  of 
the  bases.  For  the  sake  of  comparison  we  give  below  the 
theoretical  percentages  calculated  for  this  formula  and  also 
.present  How's  analysis  and  theory. 


Mean  £. 

Theory. 

Si02 

66.40 

65.72 

A1203  (Fe20s) 

11.74 

12.53 

CaO  (MgO) 

2.11 

2.27 

K20 

3.58 

3.82 

Na20 

2.27 

2.52 

H20 

13.31 

13.14 

Totals 


99.41 


100.00 


Howf. 

68.40 

12.77 

3.46 

2.35 

13.02 

100.00 


Theory. 

66.73 

12.74 

4.62 

2.56 

13.35 

100.00 


If,  instead  of  accepting  How's  formula  we  take  the  ratio 
of  the  bases  to  the  silica  as  found  by  my  analysis,  it  will  be 
seen  that  they  give  with  remarkable  exactness  RO  :  ALjO3 : 
SiO2 :  H2O  as  1:1  :  10  :  6|.  The  formula  becomes  in  this 
case  (£K2O,  JNa2O,  £CaO)  .  A12OS  .  10SiO2  .  6|H2O.  This 


180 


ON  MORDENITE. 


becomes  in  general  3RAl2Si10O24  +  20H2O,  the  three  Rs  being 
replaced  by  a  molecule  each  of  potash,  soda,  and  lime. 

In  1886,  under  the  name  of  ptilolite,  Cross  and  Eakins  * 
described  a  new  zeolite  from  Jefferson  Co.,  Colorado,  which, 
like  the  mordenite,  occurs  as  a  secondary  formation  in  a  basic 
lava.  As  the  result  of  their  investigations  they  assigned  to 
the  mineral  the  general  formula  RAl2Sii0O24  +  5H2O,  in  which 
R  consisted  of  lime,  potash  and  soda,  not  however  in  any 
simple  ratio.  The  similarity  of  these  two  formulae  is  very 
striking,  and  it  seems  evident  that  the  two  minerals  belong 
to  the  same  group  of  zeolites,  the  ratio  of  bases  and  silica 
being  the  same  in  each,  the  chief  difference  being  that  the 
ptilolite  contains  one-quarter  less  of  water.  In  the  crystal 
form  and  optical  properties,  however,  the  two  zeolites  are 
entirely  unlike. 

While  this  formula  for  mordenite  confirms  the  work  of 
Cross  and  Eakins  in  the  existence  of  these  very  acid  hydrous 
silicates,  which  can  no  longer  remain  doubtful,  and  the  theo- 
retical percentages  calculated  for  it  agree  with  very  great 
closeness  with  the  given  analysis,  it  will  be  best,  however, 
to  retain  the  composition  given  by  How  on  account  of  its 
greater  simplicity  and  because  it  differs  but  slightly  from  the 
above. 

In  the  symmetry  of  its  crystal  form 
mordenite  is  monoclinic  and  also  isomor- 
phous  with  heulandite.    The  crystal  habit 
is  shown  in  the  figure  and  is  remarkably 
similar  to  heulandite  from  Jones'  Falls, 
near   Baltimore,    Md.     The  only  forms 
observed  were   <?(001),  5(010),  Z(450), 
t  (201)  and  s  (201).     The  measurements 
were  made  on  a  Fuess  goniometer,  using 
the    8   ocular   of   Websky.      From   the 
small  size  of  the  crystals  and   poor  re- 
flections, owing  to  dulness  of  the  faces  and  to  striations  due 
to   a   repetition   of   the   crystal   form  in   parallel  position,  a 
*  Amer.  Jour.  Sci.,  1886,  vol.  32,  p.  117. 


ON  MORDENITE.  181 

considerable  series  had  to  be  examined  before  any  sharp  reflec- 
tions could  be  obtained.  No  sharp  reflections  could  be  obtained 
from  any  clinopinacoid,  since  from  the  separation  of  cleavage 
plates  it  was  invariably  too  rough  to  reflect  well.  Finally  one 
crystal  was  found  which  gave  very  fair  and  distinct  reflections 
in  the  prismatic  zone  and  from  the  orthodomes.  Another 
gave  good  reflections  in  the  zone  of  symmetry.  From  these 
the  following  angles  were  taken  as  fundamental : 

c  A  t  =  001  A  201  =  63°  40' 
t  A  s  =  201  A  20T  =  50°  12' 
s  A  I  =  20T  A  450  =  36°  07' 

and  from  these  we  calculate  the  axial  ratio 

a  :  b  :  c  =  0.40099  :  1  :  0.42792 ;  ft  =  88°  29'46". 

For  heulandite  we  have, 

a  :  b  :  c  =  0.40347  :  1  :  0.42929;  p  =  88°  34^', 

adopting  the  orientation  given  the  latter  species  by  Des 
Cloizeaux.  Only  one  other  satisfactory  measurement  could 
be  made: 

Calculated.  Measured. 

I  A  I  =  450  A  4oO  =  53°  15'  52°  44' 

52°  33' 

The  only  difference  then  between  the  mordenite  and  the 
Jones'  Falls  crystals  of  heulandite  is  that  the  prism  occurring 
on  the  latter  if  taken  as  (110)  requires  the  similar  prism  on 
the  mordenite  to  be  (450). 

The  crystals  occur  attached  at  one  end  upon  their  prismatic 
faces.  They  form  groups  from  growth  parallel  to  the  clino- 
pinacoid, and  are  also  somewhat  radially  disposed.  The 
cleavage  is  eminently  clinodiagonal  and  the  luster  of  the 
clinopinacoid  is  pearly,  so  that  cleavage  fragments  resemble 
small  nacreous  fish  scales.  Under  the  polaring  microscope, 
using  cleavage  plates  of  the  mineral  which  furnish  sections 
parallel  to  the  clinopinacoid,  it  was  found  that  the  plane  of 


182  ON  MORDENITE. 

the  optic  axes  is  normal  to  this  face.  The  direction  of  ex- 
tinction is  negative,  according  to  the  scheme  adopted  for  the 
plagioclase  feldspars  and  inclined  about  15°  to  the  clinodiag- 
onal  axis.  This  axis  of  elasticity  =  c  and  b  =  a.  The  optic 
angle  is  large  and  it  is  uncertain  whether  (  or  a  is  the  acute 
bisectrix;  the  double  refraction  is  weak,  high  polarization 
colors  being  shown  only  by  the  thickest  sections  between 
crossed  nicols,  while  thin  sections  show  gray  of  the  first 
order.  The  hardness  of  mordenite  is  about  3.  How  gives 
5  for  his  mineral.  While  it  is  difficult  to  ascertain  the  exact 
hardness  of  a  species  occurring  in  such  small  brittle  crystals 
it  was  certainly  not  so  hard  as  5,  and  3  is  believed  to  be  more 
correct.  Before  the  blowpipe  mordenite  does  not  exfoliate; 
it  gives  off  its  water  readily,  practically  without  changing  its 
form,  and  melts  with  some  difficulty  to  a  white  enamel. 


ON  THE  COMPOSITION  OF  POLLUCITE  AND  ITS 
OCCURRENCE  AT  HEBRON,   MAINE. 

BY  H.  iL.  WELLS. 
(From  Amer.  Jour.  Sci.,  1891,  vol.  41,  pp.  213-220.) 

IT  is  a  matter  of  great  satisfaction  to  announce  the  discovery 
of  pollucite  in  a  new  locality.  This  very  interesting  mineral 
has  heretofore  been  found  only  on  the  Island  of  Elba  and 
even  there  in  very  small  quantities,  so  that  it  may  be  called 
a  mineralogical  rarity.  Its  composition,  in  being  the  only 
known  mineral  in  which  caesium  is  an  essential  constituent, 
adds  greatly  to  its  interest. 

Before  describing  the  American  material,  some  account  of 
the  history  of  the  mineral  may  be  given.  In  1846,  Breithaupt 
described*  two  minerals  from  Elba,  which  he  called  Castor 
and  Pollux  from  their  great  similarity  in  appearance.  He 
distinguished  them  easily  however  by  their  difference  in  spe- 
cific gravity.  Castor  is  now  considered  to  be  identical  with 
petalite,  and  it  is  a  fact  worthy  of  mention  that  the  latter 
mineral  is  found  at  Peru,  Maine,  only  a  few  miles  from  the 
new  pollucite  locality,  a  fact  which  points,  perhaps,  to  a  new 
association  of  "Castor  and  Pollux."  Breithaupt's  material 
was  analyzed  by  Plattner,f  but  at  that  time  caesium  had  not 
been  discovered,  so  that  he  naturally  mistook  it  for  potassium. 
His  results  were  as  follows  : 


1. 

Si02 

Plattner. 

46.200 

A1203 
Fe203 

16.394 

0.862 

K20 

16.506 

Na20  t 

10.470 

H2O 

2.321 

92.753 
*  Pogg.  Ann.,  Ixix,  439.  t  Ibid.,  p.  446.  \  With  trace  of  Li2O. 


184  COMPOSITION  OF  POLLUCITE. 

Plattner  sought  in  vain  for  an  explanation  of  his  low  results, 
and  not  having  enough  material  to  repeat  his  analysis,  he 
published  it  as  it  was.  The  discrepancy  remained  unex- 
plained until  in  1864,  eighteen  years  later,  and  after  Plattner's 
death,  Pisani*  discovered  caesium  in  the  mineral.  Pisani 
states  that,  if  Plattner's  analysis  be  recalculated  on  the  sup- 
position that  the  caesium  was  weighed  as  platinichloride  while 
the  soda  was  calculated  in  the  usual  way  from  the  weight  of 
the  mixed  chlorides,  that  the  results  would  correspond  closely 
to  his  own  analysis.  Brush  afterwards  published  a  recalcu- 
lation f  on  this  assumption,  which  is  given  below  under  la. 
Since  Plattner  used  0.5  gram  of  substance  for  his  analysis, 
the  footing  still  hardly  does  justice  to  his  well-known  skill  as 
an  analyst.  I  have  therefore  made  a  new  recalculation,  given 
under  15,  assuming  that  Plattner's  platinichlorides  contained 
enough  potassium  to  make  an  exact  summation.  This  as- 
sumption is  warranted  to  a  certain  extent  by  the  fact  that 
all  analyses  of  pollucite  since  Plattner's  give  at  least  a  trace 
of  potash.  This  calculation  of  the  potash  cannot  be  consid- 
ered very  exact,  but  it  is  quite  probable  that  a  part  of  the 
excess  shown  by  the  other  recalculation  was  due  to  the 
presence  of  this  substance. 

la.  ib. 


Plattner,  Wotin  Plattner.  ,,  ... 

Recalculated.  Recalculated. 

Si2O      46.20  0.770  or  4.64  Si02      46.20  0.770  or  4.64 

A1203    16.39    0.161)  Ai263    16.39    0.161  )-___ 

Fe203      0.86    0.005  r166or1-00  FeA      0.86    0.005  T'166  °r  1X)0 

Cs2O      35.69    0.127  \  Cs2O      29.80    0.106  \ 

K20        [  0.155  or  0.93  K2O         2.71    0.029  >  0.163  or  0.98 

Na2O       1.72    0.028)  Na20       1.72    0.028) 

H2O        2.32  0.129  or  0.78  H20         2.32  0.129  or  0.78 

103.18  100.00 

The  analysis  which  Pisani  made  on  his  discovery  of  caesium 
in  the  mineral,  is  as  follows : 

*  C.  B.  Iviii,  714.  f  Amer.  Jour.  Sci.,  1864,  vol.  38,  p.  115. 


COMPOSITION  OF  POLLUCITE.  185 

2.  2  a. 


Pisani. 

Ratio  with 
w_«_                     assumed  correction 
(Na20  =  2.17  per 

cent). 

Si02 

44.03 

0.734  or  4.56 

0.734  or  4.56 

A1203 
Fe203 

15.97 
0.68 

0.157  ; 
0.004  ! 

[•  0.161  or  1.00 

0.161  or  1.00 

CaO 

0.68 

0.012 

) 

Cs20* 

34.07 

0.121  j 

>  0.196  or  1.22 

0.168  or  1.04 

Na20* 

3.88 

0.063  . 

I 

H2O 

2.40 

0.133  or  0.83 

0.133  or  0.83 

101.71 

Pisani  is  very  positive  about  the  freedom  of  his  csesia  from 
any  considerable  amount  of  potash,  and  he  determined  the 
atomic  weight  of  his  alkali-metal  in  support  of  this ;  hence  it 
is  scarcely  allowable  to  recalculate  his  analysis,  as  has  been 
done  in  the  case  of  Plattner's,  with  the  assumption  that  the 
excess  was  due  to  the  presence  of  potash.  It  is  the  author's 
opinion,  from  a  consideration  of  one  of  Rammelsberg's  analyses 
which  will  be  mentioned  later  and  of  the  analyses  of  the  new 
material  from  Maine,  that  Pisani's  excess  was  at  least  largely 
due  to  too  much  soda,  either  derived  from  glass  vessels  or 
from  some  other  cause,  hence  a  ratio  is  given  under  2a  above, 
after  deducting  1.71  per  cent  of  soda  from  the  analysis. 
Pisani  deduced  from  his  analysis  the  oxygen  ratio,  SiO2 : 
Al2(Fe2)O3 :  Csa(CaiNa,)O  :  H2O  =  15  :  5  :  2  :  2.  This  ratio 
would  be  expressed  by  the  very  complicated  formula,  45SiO2  . 
10A1203  .  12Cs20  .  12H20. 

Pisani  certainly  left  the  question  of  the  true  composition  of 
pollucite  open  to  doubt,  and  in  1878  Rammelsberg  published! 
a  new  analysis  of  the  mineral  with  the  view  of  clearing  up 
the  doubt.  Rammelsberg's  material  was  evidently  not  well 
adapted  to  the  purpose  of  determining  the  composition  of  the 
mineral,  for  he  first  picked  from  it  some  pieces,  "  more  or  less 
translucent,"  and  obtained  from  them,  A12O3  16.58,  alkalies 
precipitated  by  platinic  chloride  23.03,  Na2O  2.00,  Li2O  0.83 ; 
then  he  picked  from  the  same  material  some  fragments  which 

*  With  traces  of  K20  and  Li20.  t  Berlin.  Akad.,  9, 1878. 


186  COMPOSITION  OF  POLLUCITE. 

had  a  specific  gravity  of  2.868,  the  lowest  number  which  has 
ever  been  given  for  the  mineral,  although  Breithaupt  gives 
the  same  number  as  the  lowest  of  a  series,  and  he  made  the 
following  analysis  from  it : 


Rammelsberg, 
First  analysis. 

Ratio. 

Si02 

[48.15] 

[0.802  or  5.01] 

A1208 

16.31 

0.160  or  1.00 

Cs20 

30.00 

0.106  ) 

K20 

0.47 

0.006V   0.151  or  0.94 

Na20 

2.48 

0.040  ) 

H20 

2.59 

0.144  or  0.90 

100.00 

On  this  single  analysis,  where  an  important  constituent  was 
determined  by  difference  and  where  the  material  was  of 
questionable  purity,  Rammelsberg  obtains  the  formula  which 
is  now  generally  accepted  for  the  mineral.  The  analysis  cor- 
responds to  the  formula  H2R'2Al2(SiO8)6 ;  Rammelsberg  in- 
cludes the  hydrogen  in  R'  and  writes  it  R'4Al2(SiO8)5. 

It  may  be  inferred  that  Rammelsberg  himself  was  not  fully 
satisfied  with  his  results,  for  about  two  years  later,  he  pub- 
lished *  an  analysis  of  what  he  describes  as  the  purest  material. 
This  analysis  is  given  below. 


Rammelsberg,  Ratio  from  the 

New  analysis.  mean  of  4. 


** 

I. 

II. 

III. 

SiOo 

46.48 

0.775  or  4.58  or  9.16 

K.7J.V/2 

A1208 

17.24 

.  .  . 

0.169  or  1.00  or  2.00 

Cs20 

.  .  . 

30.71 

30.53 

0.109 

> 

K20 

.  .  . 

0.78 

0.41 

0.006  ] 

>  0.151  or  0.89  or  1.78  < 

) 

Na20 

2.31 

2.19 

0.036  . 

1               ! 

>3.30 

H20 

2.32 

.  .  . 

.  .  . 

0.129  or  0.76  or  1.52  3 

} 

He  does  not  publish  any  ratio  with  this  analysis,  but  says : 
"  These  results  confirm  the  former."  The  emphasis  is  Ram- 
melsberg's.  It  may  be  noticed,  however,  that  this  analysis 

*  Berlin.  Akad.,  671,  1880. 


COMPOSITION  OF  POLLUCITE.  187 

corresponds  very  closely  to  the  formula,  9SiO2  .  2A12O3  . 
2R'2O  .  1^H2O,  or  putting  in  H  with  R',  it  corresponds  very 
well  with  the  metasilicate  formula,  R/6Al4(SiO3)9.  Moreover 
the  formulae  just  mentioned  correspond  much  better  with  the 
analyses  of  Plattner  and  Pisani  than  Rammelsberg's  formula 
does.  What  the  probable  formula  for  pollucite  is,  will  be  dis- 
cussed after  giving  the  analysis  of  the  Hebron  mineral. 

The  locality,  Hebron,  from  which  the  new  material  comes, 
furnished  the  lepidolite  from  which  Allen  *  extracted  a  large 
quantity  of  caesium  and  rubidium,  the  material  used  by 
Johnson  and  Allen  f  in  determining  the  atomic  weight  of 
caesium  as  now  accepted.  Hebron  also  furnished  the  remark- 
able beryl  in  which  Penfield  J  found  2.92  per  cent  of  caesium 
oxide.  It  might  have  been  expected,  therefore,  that  this 
locality  would  be  likely  to  furnish  pollucite ;  indeed,  Professor 
Brush  tells  me  that  he  has  tested  a  large  quantity  of  quartz 
fragments  from  the  locality,  hoping  that  some  of  them  might 
be  this  mineral. 

The  specimens  were  found  during  the  past  summer  by  Mr. 
Loren  B.  Merrill,  of  Paris,  Me.,  and  a  few  pieces  were  sent  by 
him  for  identification  to  Professor  Brush,  who  very  kindly 
gave  them  to  the  author  for  examination.  Mr.  Merrill  has 
since  very  generously  loaned  us  his  whole  stock  of  the  mineral, 
amounting  to  more  than  half  a  kilogram,  in  order  that  a 
thorough  examination  might  be  made.  The  mineral  is  said  by 
the  discoverer  to  have  been  found  in  only  two  cavities.  In 
one  of  these  only  two  or  three  pieces  were  found,  associated 
with  large,  etched  quartz  crystals.  In  the  other  cavity  the 
main  part  of  the  mineral  was  found  in  a  loose  heap  mixed 
with  clay.  This  last  cavity  was  open  at  the  top,  and  was 
three  feet  wide,  six  feet  long,  and  eighteen  inches  deep.  It 
was  associated  with  quartz,  a  crystal  of  which  was  in  one  case 
imbedded  in  the  pollucite,  also  with  psilomelane  and  with 
another  mineral  which  proves  to  be  a  nearly  colorless,  brilliant 
caesium-beryl.  The  pollucite  was  in  the  form  of  irregular 

*  Amer.  Jour.  Sci.,  1862,  vol.  34,  p.  367.          t  Ibid.,  1863,  vol.  35,  p.  94. 
}  Ibid.,  1884,  vol.  28,  p.  29. 


188  COMPOSITION  OF  POLLUCITE. 

fragments,  mostly  between  J  and  10  grams  in  weight,  very 
similar  to  those  figured  by  Breithaupt  in  his  original  descrip- 
tion of  the  mineral  from  Elba.  The  substance  of  many  of 
the  fragments,  such  as  were  used  for  the  analysis,  was  of  the 
most  perfect  physical  character,  perfectly  colorless  and  as 
brilliant  and  transparent  as  the  finest  glass. 

Professor  S.  L.  Penfield  has  kindly  made  the  following 
report  of  an  optical  examination  of  the  substance: 

"  Refractive  indices  on  a  prism  of  43°  41' : 

n  =  1.5215  Li 
n  =  1.5247  Na 
n  =  1.5273  Tl 

"  The  mineral  shows  no  double  refraction,  hence  it  is  iso- 
metric. Under  the  microscope  it  is  very  free  from  inclusions. 
Some  of  the  specimens  show  a  series  of  holes,  in  parallel 
position,  extending  into  the  substance  of  the  fragment  at 
right  angles  to  its  surface.  These  holes  have  rectangular 
cross-sections  and  they  give  to  some  of  the  specimens  a  sort 
of  fibrous  structure."  Unfortunately,  none  of  the  fragments 
have  any  distinct  crystalline  faces. 

In  its  pyrognostic  properties,  its  luster  and  hardness,  and 
its  lack  of  any  apparent  cleavage,  it  agrees  exactly  with  the 
observations  of  Breithaupt,  Plattner,  and  the  other  observers 
in  regard  to  the  Elba  mineral.  It  is  completely,  though 
slowly,  decomposed  by  hydrochloric  acid  with  the  separation 
of  pulverulent  silica.  This  agrees  with  the  observations  of 
Plattner  and  Pisani,  but  not  with  the  statements  of  Ram- 
melsberg.  The  latter  was  doubtless  deceived  by  the  slow- 
ness of  the  action,  for  it  takes  several  hours  to  decompose 
the  finely  pulverized  mineral  with  moderately  concentrated 
acid  at  the  heat  of  the  water-bath. 

The  specific  gravity  of  the  Hebron  mineral  was  taken 
twice  on  each  of  two  fragments ;  one  gave  2.985  and  2.987, 
the  other  2.976  and  2.977.  It  will  be  noticed  that  the  Maine 
mineral  is  considerably  heavier  than  that  from  Elba.  Breit- 
haupt gives  2.868,  2.876,  2.880  and  2.892;  Pisani  gives 


COMPOSITION  OF  POLLUCITE.  189 

2.901 ;  Rammelsberg  gives  for  the  material  used  in  his  first 
analysis  2.868,  and  for  the  pure  material  used  in  his  second, 
2.885  to  2.896.  All  of  this  European  material,  except  that 
used  by  Rammelsberg  for  his  first  analysis,  is  described  by 
the  various  observers  as  being  colorless  and  transparent. 
The  indications  are  that  the  higher  specific  gravities  represent 
the  better  material,  and  the  comparatively  high  specific  gravity 
of  the  American  mineral  seems  to  point  to  still  better  quality  if 
not  to  some  difference  in  composition. 

A  single  piece  of  the  very  best  quality  was  selected  for 
the  chemical  examination,  while  the  water  was  determined 
in  two  other  fragments  also,  because  of  the  evident  import- 
ance of  the  water  in  calculating  the  formula.  Analyses  I  and 
II  were  first  made,  but,  as  they  did  not  show  a  perfect  agree- 
ment in  the  determinations  of  the  alkalies,  No.  Ill  was  then 
made  with  the  greatest  care.  This  last  is  considered  the  best 
of  the  analyses  and  the  ratio  given  is  calculated  from  it,  but 
it  will  be  noticed  that  the  other  two  analyses  confirm  this 
quite  well  and  that  they  both  point  to  the  same  formula  with 
almost  equal  sharpness. 

Water  was  determined  by  loss  by  ignition,  as  given  in 
detail  beyond ;  the  "  intense  ignitions "  were  made  in  small 
platinum  crucibles  over  a  powerful  blast-lamp  flame,  so  that 
the  heat  obtained  was  very  high.  The  material  was  not 
dried  in  any  way  before  weighing.  The  mineral  was  decom- 
posed by  hydrochloric  acid,  and  silica,  alumina,  and  lime  were 
determined  by  the  usual  methods,  care  being  taken  to  take 
account  of  the  slight  impurities  in  the  silica  and  alumina. 
The  alumina  contained  a  very  faint  trace  of  iron,  no  more 
than  might  have  been  introduced  by  breaking  the  mineral  up 
with  steel  cutters ;  no  evidence  could  be  found  of  the  presence 
of  other  elements  in  the  alumina.  The  identity  of  the  lime 
was  shown  by  the  spectroscope. 

The  alkali-metals  were  weighed  together  as  chlorides,  then 
caesium  and  potassium  were  separated  and  weighed  as  platini- 
chlorides ;  the  alkali-chlorides  in  the  latter  were  separated  and 
weighed  in  order  to  calculate  the  proportion  of  csesia  and 


190 


COMPOSITION  OF  POLLUCITE. 


potash.  The  potassium  spectrum  was  detected  from  these 
last  chlorides  with  considerable  difficulty,  while  they  showed 
no  rubidium  spectrum  whatever.  Lithium  chloride  was  sepa- 
rated from  sodium  chloride,  after  the  removal  of  the  excess 
of  platinum,  by  the  method  of  Gooch,  and  the  soda  was  cal- 
culated from  the  difference  between  the  other  chlorides  and 
the  total  mixed  chlorides,  while  in  analysis  III  the  sodium 
chloride  was  also  weighed  directly,  giving  a  result  which 
happened  to  be  exactly  identical  with  the  indirect  determi- 
nation. This  agreement  of  the  direct  with  the  indirect  de- 
termination of  the  soda  may  be  considered  as  an  indication 
that  the  other  alkalies  were  determined  with  reasonable  accu- 
racy. The  lithium  was  identified  with  the  spectroscope. 
The  following  are  the  results  of  the  analyses : 


Single  piece. 


Two  separate  pieces. 


Weight  of  substance  taken  .  .    0.6260 
Loss  by  heating  at  125°-130° 
Loss  by  heating  at  165°-170° 
Loss  by  heating  to  red  heat   . 
Loss  by  intense  ignition    .  .  . 

H20 

Si02 


CaO 

Cs20 36.77 

K2O 

Na20 

Li20 


I. 

II. 

in. 

IV. 

V. 

0.6260 

1.1291 

0.9491 

1.0205 

1.4826 

0.00 

. 

0.03 

0.01 

1.49 

.  .  . 

1.50 

1.56 

1.50 

0.04 

.  .  . 

0.02 

0.03 

1.53 

[1.53] 

1.50 

1.58* 

1.53* 

43.48 

43.59 

43.51 

16.41 

16.39 

16.30 

0.21 

0.22 

0.22 

36.77 

35.36 

36.10 

0.47 

0.51 

0.48 

1.72 

2.03 

1.68 

0.03 

0.04 

0.05 

100.62       99.67        99.84 


The  ratio  calculated  from  No.  Ill,  and  the  calculated  com- 
position, giving  the  alkalies  the  same  proportion  as  in  the 
analysis,  but  omitting  lime  and  lithia  as  insignificant,  is  given 
beyond : 

*  Not  including,  respectively,  0.03  and  0.01  per  cent  of  water  lost  at  165°- 
170°. 


COMPOSITION  OF  POLLUCITE. 


191 


Hebron  Pollucite. 
Ratio  from  analysis  III. 

Calculated  for 
<R>-&*cf^SiS3^N^ 

(R  —  ie§  Cs,  T|0  K,  ffo  Na). 

Si02  ....  43.55 

Si02. 

0.725 

or  4.53 

or  9.06 

A1208 

0.160 

1.00 

2.00 

A1203 

.  .  .  16.45 

CaO  . 

.  .  .  0.004 

Cs2O 

.  .  .  36.38 

Cs20 

.  .  .  0.128 

K20. 

.  .  .     0.48 

K20. 

.  .  .  0.005 

>  0.166 

1.04 

2.08 

Na20 

.  .  .    1.69 

Na20 

.  .  .  0.027 

H20. 

.  .  .     1.45 

Li20. 

.  .  .  0.002  . 

H20. 

0.083 

0.52 

1.04 

100.00 

The  sharpness  of  the  ratio  and  the  agreement  of  the  analysis 
with  the  calculated  composition  are  all  that  could  be  desired. 
There  can  be  no  doubt,  then,  that  the  composition  of  the 
Hebron  mineral  is  represented  by  the  formula  9SiO2 .  2A12O3  . 
2R'2O  .  H2O  or  H2R'4Al4(SiO3)9.  The  theoretical  composition 
for  H2Cs4Al4(SiO3)9,  supposing  no  alkalies  except  Cs2O  to  be 
present,  is, 

Si02 40.72 

A12O3 15.39 

Cs20 42.53 

H20 1.36 

100.00 

A  comparison  of  all  the  ratios  given  in  this  article,  as 
shown  in  the  following  table,  makes  it  probable  that  the  new 
formula  can  be  assigned  also  to  the  Elba  mineral.  The 
ratios  have  been  calculated  with  A12O3  as  unity  because  it 
shows  less  variation  throughout  the  analyses  than  the  other 
constituents. 

Leaving  out  of  consideration  Rammelsberg's  first  analysis, 
there  can  be  little  doubt  that  the  new  formula  expresses  the 
composition  of  Elba  pollucite  as  far  as  the  first  three  members 
of  the  ratios  are  concerned,  but  the  water  is  0.8-0.9  per  cent 
higher  in  the  analyses  of  that  material  than  the  formula 
requires.  A  part  of  this  excess  may  be  accounted  for  by 
supposing  it  to  take  the  place  of  any  deficiency  in  the  alkalies, 
as  will  be  noticed  especially  in  the  last  analysis  of  Ram- 


192 


COMPOSITION  OF  POLLUCITE. 


Ratios. 


Plattner's  analysis  as  recalculated  by  Brush 
Plattner's  analysis  newly  recalculated   .  .  . 

Pisani's  analysis 4.56 

Pisani's  analysis  with  assumed  correction  .  . 
Rammelsberg's  analysis  on  which  he  based  his 

formula [5.01] 

Kammelsberg's  later  analysis     4.58 

Analysis  of  Hebron  pollucite 4.58 

Proposed  formula  requires 4.50 

Kammelsberg's  formula  requires 5.00 

Or,  as  he  writes  the  latter 5.00 


>i02 

Al203(Fe203) 

:  R'20  :  H2O. 

64 

1.00 

:  0.98  :  0.78 

64 

1.00 

0.98  :  0.78 

56 

1.00 

1.22  :  0.83 

56 

1.00 

1.04  :  0.83 

01] 

1.00 

0.94  :  0.90 

58 

1.00 

0.89  :  0.76 

53 

1.00 

1.04  :  0.52 

50 

1.00 

1.00  :  0.50 

DO 

1.00 

1.00  :  1.00 

)0 

1.00     : 

2.00 

melsberg;  hence,  since  the  small  excess  of  water  cannot  be 
introduced  into  the  formula  without  complicating  it  greatly 
and  destroying  the  metasilicate  ratio,  it  is  probably  best  to 
consider  it  as  accidental.  The  replacement  of  a  small  part  of 
the  alkalies  by  water  in  the  Elba  mineral  would  explain  its 
lower  specific  gravity. 

It  is  satisfactory  to  notice  that  the  historical  first  analysis 
by  Plattner  confirms,  in  each  of  its  recalculated  forms,  the 
conclusions  arrived  at  in  this  paper. 


THE   CHEMICAL  COMPOSITION  OF  IOLITE. 

BY  O.  C.  FARRINGTON. 
(From  Amer.  Jour.  Sci.,  1892,  vol.  43,  pp.  13-16.) 

As  is  well  known,  the  formula  of  iolite  has  never  been  satis- 
factorily established.  This  is  chiefly  for  the  reason  that 
the  state  of  oxidation  of  the  iron,  in  the  analyses  hitherto 
published,  has  not  been  determined.  Stromeyer,*  Gmelin  f 
and  Schutz,:f  who  made  the  earlier  analyses,  regarded  the  iron 
as  protoxide.  Scheerer,§  however,  in  1846,  in  connection 
with  analyses  of  iolite  from  Kragero,  urged  that  it  was  more 
probably  present  as  sesquioxide,  his  reason  being  stated  as 
follows : 

"Das  Verhaltniss  des  Sauerstoffs  der  Kieselerde  zu  dem  der 
Thonerde  und  zu  dem  der  1  und  1  atomigeii  Basen  ergiebt  sich 
hiernach  wie :  Si03  26.20  :  A12O3  15.26  :  EO  5.48  wenn  man 
namlich  annimmt,  dass  die  geringe  Menge  Eisen  als  Oxydul  im 
Mineral  vorhanden  sei.  Diess  diirfte  aber  schwerlich  der  Fall 
sein,  da  der  analysirte  Cordierit  fast  vollig  farblos  war  und  auch 
nicht  den  geringsten  Stich  ins  Griinliche  zeigte,  wahrend  es 
bekannt  ist,  dass  verhaltnissmassig  sehr  kleine  Quantitaten  Eisen- 
oxydul  hinreichend  sind,um  einen  (nicht  pulverformigen)  Silicate 
eine  deutlich  grtine  Farbe  zu  ertheilen,  sobald  diess  nattirlich 
nicht  durch  andere  farbende  Substanzen  verhindert  wird.  Mmmt 
man  daher  gewiss  init  mehr  Recht  das  Eisen  in  Zustande  des 
Oxyds  an,  so  wird  das  Sauerstoffverhaltniss  Si03  26.20  :  R203 
15.64  :  RO  5.26." 

This  conclusion  of  Scheerer  has  been  accepted  by  most  later 
writers.  Rammelsberg,  ||  regarding  the  iron  as  sesquioxide, 

*  Unters.,  Rg.  Min.  Ch.  f  Schweigger's  J.,  xiv,  316. 

I  Pogg.  Ann.,  liv,  p.  565.  §  Pogg.  Ann.,  Ixviii,  p.  319. 

||  Mineralchemie,  1875,  p.  652. 
13 


194  CHEMICAL   COMPOSITION  OF  IOLITE. 

deduces  the  generally  accepted  formula,  2MgO  .  2R2O3  .  SSiOa, 
although  the  ratios  are  not  very  satisfactory.  He  also  sug- 
gests MgsReSisOas  as  a  possible  formula.  Water  seems  to 
have  been  disregarded. 

At  the  locality  in  Guilford,  Conn.,  recently  described  by 
Dr.  E.  O.  Hovey,*  iolite  occurs  as  stated  by  him,  as  a  constit- 
uent of  the  rock  mass.  This  locality  was  visited  by  the 
writer,  and  it  was  also  found  that  veins  of  more  coarsely 
crystalline  material  running  through  the  gneiss,  contained  the 
mineral  in  grains  as  large  as  a  walnut  and  even  in  pieces 
of  sufficient  size  for  hand  specimens.  These  large  grains  are 
very  clear  and  transparent,  and  show  none  of  the  tendency  to 
alteration  so  characteristic  of  the  iolite  from  other  localities. 

The  exceptional  purity  of  this  material  led  the  writer  to 
make  a  chemical  analysis  of  it,  and  care  was  taken  to  use 
only  those  grains  which  were  perfectly  clear  and  showed  the 
characteristic  pleochroism  of  the  mineral.  A  determination 
of  the  state  of  oxidation  of  the  iron  was  included  in  the 
analysis,  FeO  being  determined  by  decomposition  of  a  separate 
portion  with  hydrofluoric  and  sulphuric  acids  and  titration  with 
potassium  permanganate.  Water  was  determined  directly, 
by  fusing  about  a  gram  of  the  mineral  with  dry  sodium 
carbonate  in  a  Gooch  tubulated  crucible  and  collecting  in  a 
chloride  of  calcium  tube.  The  precaution  was  taken  to 
surround  the  first  crucible  with  another  containing  sodium 
carbonate,  so  that  no  products  of  combustion  from  the  flame 
could  penetrate  the  red-hot  platinum  and  render  the  result 
too  high.  The  analysis  gave  the  following  results: 

.  5.00 
198 


2.03 
0.54 


I. 

II. 

Mean. 

Ratio. 

Si02 

49.44 

49.56 

49.50 

0.825 

0.825 

A1203 

32.97 

33.04 

33.01 

0.324  i 

1 

Fe203 

0.35 

0.41 

0.38 

0.002  ! 

I 

FeO 

5.11 

5.13 

5.12 

0.071  - 

) 

MnO 

0.32 

0.27 

0.29 

0.004  1 

>  0.335 

MgO 

10.39 

10.46 

10.42 

0.260  ! 

1 

H20 

1.65 

1.58 

1.62 

0.090 

0.090 

100.23 

100.45 

100.34 

Sp.  Gr.  2.607 

*  Amer.  Jour.  Sci.,  1888,  vol.  36,  p.  57. 


CHEMICAL   COMPOSITION  OF  IOLITE.  195 

From  this  it  will  be  seen  that  nearly  all  of  the  iron  is 
present  as  protoxide.  The  analysis  also  shows  the  ratio  of 
SiO2  :  R2O3  :  RO  :  H2O,  to  be  very  nearly  5:2:2:  0.5. 

In  order  to  test  these  results  by  comparing  different  material, 
an  analysis  was  also  made  of  iolite  from  the  well  known  local- 
ity at  Haddam,  Conn.,  the  specimens  being  very  kindly  fur- 
nished by  Professor  Brush  from  his  private  collection. 

This  analysis  resulted  as  follows  : 

Ratio. 
0.819    0.819  5.00 


I. 

II. 

Mean. 

Si02 

49.25 

49.03 

49.14 

A1203 

32.81 

32.87 

32.84 

Fe20 

0.58 

0.67 

0.63 

FeO 

5.06 

5.01 

5.04 

MnO 

0.19 

0.19 

0.19 

MgO 

10.51 

10.30 

10.40 

H20 

1.81 

1.88 

1.84 

100.21 

99.95 

100.08 

Sp.  Gr. 

2.610 

0.070  j 

0.003  [  0.333  2.03 

0.260  ) 

0.102    0.102  0.62 


Here  the  percentages  of  Fe2O3  and  H2O  are  slightly  larger 
than  in  the  other  analysis,  but  this  might  almost  be  expected 
on  account  of  the  strong  tendency  of  the  Haddam  mineral  to 
alteration.  The  ratios,  however,  as  will  be  seen,  are  almost 
exactly  the  same  as  those  given  by  the  Guilford  mineral. 
The  formula  of  iolite  is  therefore  H2O  .  4(Mg,  Fe)O  .  4A12O3. 
10SiO2,  the  ratio  of  MgO  :  FeO  being  in  these  two  analyses 
very  nearly  7  :  2.  The  theoretical  percentages  according  to 
this  formula  are  given  below,  and  for  comparison,  the  mean  of 
each  of  the  two  analyses  calculated  to  100  per  cent,  the  small 
quantities  of  Fe2O3  and  MnO  being  reckoned  as  A12O8  and 
MgO  respectively. 

m,  . Calc.  to  100. , 

Guilford.  Haddam. 

10Si02  49.40 

4A1303  33.60 

|(4FeO)  5.27 

J(4MgO)  10.25 

H20  1.48 

100.00          100.00          100.00 


196  CHEMICAL    COMPOSITION  OF  IOLITE. 

These  results  show  satisfactory  agreement,  and  the  per- 
centages, it  may  be  said,  do  not  differ  materially  from  those 
of  the  hitherto  published  analyses  except  in  the  state  of  oxi- 
dation of  the  iron.  The  fact  that  the  iron  is  present  as  FeO, 
in  spite  of  the  lack  of  green  color,  which  caused  Scheerer's 
conclusion  to  the  contrary,  shows  how  little  reliance  is  to  be 
placed  on  color.  Indeed,  in  a  recent  description  of  colorless 
iolite  from  Brazil,*  Dr.  Groth  expresses  the  belief  that  the 
usual  violet  color  of  the  mineral  must  be  merely  due  to  a 
pigment  and  not  to  any  essential  constituent.  For  the  pur- 
pose of  determining  the  nature  of  the  water,  about  a  gram 
of  the  Guilford  mineral  was  subjected  to  increasing  tempera- 
tures until  constant  weights  were  obtained  at  each.  The 
results  were  as  follows  : 


1000  C.  3000  C.  Total. 

Loss  in  weight  None  0.63  0.87  0.10  1.60 

Up  to  full  redness  the  mineral  remained  light  in  color  but 
on  further  heating,  over  the  blast  lamp,  it  turned  black,  baked 
together  and  showed  a  slight  increase  in  weight,  owing  doubt- 
less to  oxidation  of  the  iron. 

It  will  be  seen  that  the  percentage  lost  by  heating  to  full 
redness  is  the  same  as  that  of  water  found  by  actual  determi- 
nation. Hence  loss  by  ignition  at  this  degree  of  temperature 
can  safely  be  taken  as  representing  the  amount  of  water. 
In  the  Haddam  iolite  it  was  therefore  determined  in  this  way. 
It  is  possible  that  too  low  ignition  may  account  for  the 
small  percentage  of  water  (0.50  per  cent)  found  by  Jackson 
in  one  of  his  analyses.  All  other  analyses  thus  far  published 
show  amounts  of  water  between  1  and  2.5  per  cent,  the  aver- 
age from  six  analyses  being  1.74  per  cent. 

The  high  temperature  required  to  drive  off  the  water  shows 
that  it  is  practically  all  constitutional.  If  present  as  hy- 
droxyl,  it  is  possible  that  it  combines  with  Mg  to  form  the 
univalent  radical  (MgOH).  The  recent  investigations  by 

*  Zeitschr.  Kryst.,  vol.  vii,  p.  594. 


CHEMICAL   COMPOSITION  OF  IOLITE.  197 

Clarke  and  Schneider  *  seem  to  indicate  that,  if  the  above 
molecule  is  present  in  a  silicate,  it  can  be  decomposed  by  the 
action  of  dry  HC1  gas,  so  that  an  equivalent  of  MgCl2  can 
be  dissolved  out  by  water.  An  experiment,  conducted  to 
test  this  point,  gave  no  satisfactory  results.  About  a  gram 
of  the  mineral  was  heated  in  a  current  of  the  dry  gas  for  8 
hours  and  nearly  constant  weight  was  attained.  On  leaching, 
however,  with  water  and  a  drop  of  nitric  acid,  only  0.14  per 
cent  of  MgO  went  into  solution,  so  that  no  definite  conclusion 
could  be  drawn  from  this  result. 

On  digesting  a  sample  with  strong  aqueous  HC1  for  three 
days,  on  the  water  bath,  the  following  results  were  obtained : 

Ratio  to  per  cent  in 
complete  analysis. 

Undecomposed  mineral  ....  23.20 

Si02 36.79  0.75 

A1203  with  Fe203 30.50  0.78 

MgO  with  MnO 8.04  0.77 

H02 1.84 

100.37 

From  the  above  it  is  seen  that  about  76  per  cent  of  the 
mineral  had  dissolved  and  since  the  different  constituents 
were  about  equally  affected,  it  seemed  probable  that  by  longer 
treatment  the  mineral  could  be  completely  decomposed. 
Accordingly  another  sample  was  digested,  on  the  water  bath, 
for  fifteen  days.  The  result  showed  the  supposition  to  be 
correct,  since  the  insoluble  residue  was  found  to  be  49.95  per 
cent  or  very  nearly  the  percentage  of  SiO2  in  the  mineral. 
The  mineral  therefore  is  completely  decomposed  by  long 
treatment  with  hydrochloric  acid. 

In  conclusion  the  author  wishes  to  express  his  especial 
indebtedness  to  Professor  S.  L.  Penfield,  for  much  valuable 
assistance  and  advice  rendered  during  the  work. 

*  Amer.  Jour.  Sci.,  1890,  vol.  40,  p.  303. 


ON  ARGYRODITE  AND   ITS    OCCURRENCE  AT  A 
NEW   LOCALITY  IN   BOLIVIA. 

BY  S.   L.  PENFIELD. 
(From  Amer.  Jour.  Sci.,  1893,  vol.  47,  pp.  107-113.) 

NOTE.  —  The  title  of  this  article  as  originally  published  was 
as  follows :  u  On  Canfieldite  a  new  Germanium  Mineral  and  on 
the  Chemical  Composition  of  Argyrodite."  As  will  be  shown, 
the  crystallization  of  the  mineral  from  Bolivia  is  isometric,  and 
that  from  the  original  locality  in  Freiberg,  in  Saxony,  having 
been  described  as  monoclinic  it  was  supposed  that  the  two  min- 
erals were  dimorphous ;  hence  the  name  Canfieldite  was  assigned 
to  the  isometric  variety.  It  was  afterwards  shown  that  the 
Freiberg  argyrodite  is  isometric  and  not  monoclinic;  hence  the 
name  Caufieldite  was  transferred  to  the  isomorphous  tin  com- 
pound, subsequently  discovered.  See  page  242. — EDITOR. 

IT  is  with  great  pleasure  that  the  author  is  able  to  announce 
the  discovery  of  a  new  mineral  containing  germanium  and  to 
record  the  occurrence  of  this  rare  and  interesting  element 
from  a  new  locality.  The  credit  of  this  is  due  in  great  mea- 
sure to  the  keen  mineralogical  interest  of  Mr.  Frederick  A. 
Canfield,  of  Dover,  N.  J.,  to  whom,  while  on  a  business  trip 
in  Bolivia,  South  America,  some  specimens  of  this  mineral 
were  given  as  samples  of  a  rich  and  unknown  silver  ore,  by 
friends  connected  with  the  mining  industry.  These  were 
brought  to  the  writer  for  identification  and  he  takes  great 
pleasure  here  in  acknowledging  his  indebtedness  to  Mr.  Can- 
field  and  in  expressing  his  thanks  to  him  for  the  liberality 
with  which  he  has  placed  an  abundant  supply  of  this  valuable 
material  at  his  disposal.  It  is  in  acknowledgment  of  these 
services  that  the  mineral  has  been  named  after  him. 

It  is  unfortunate  that  at  the  present  no  further  information 
can  be  given  concerning  the  exact  locality  and  mode  of 


ON  ARGYRODITE  FROM  BOLIVIA.  199 

occurrence,  but  from  inquiries  that  have  been  set  on  foot  by 
Mr.  Canfield  it  is  hoped  that  full  data  concerning  these  points 
may  be  given  later. 

When  the  mineral  was  brought  to  the  writer,  attempts 
made  to  identify  it  at  once  showed  that  it  was  not  one  of  the 
ordinary  silver  minerals.  Thus  in  the  open  tube  it  gave  a 
reaction  for  sulphur  but  no  sublimate.  In  the  closed  tube 
with  a  Bunsen  burner  flame  only  a  slight  sublimate  of 
sulphur,  but  at  a  higher  temperature  with  a  blowpipe  flame 
the  sulphur  increased,  while  nearer  the  assay  a  pale  yellow 
sublimate  formed,  which  became  lighter  on  cooling.  On 
examining  this  with  a  lens  it  was  found  to  consist  of  minute 
globules,  most  of  which  were  nearly  colorless  but  some  were 
yellow.  Boiling  concentrated  nitric  acid  was  found  to  attack 
and  oxidize  the  mineral  very  slowly.  On  charcoal  in  the 
oxidizing  flame  it  fused  readily  and  gave  almost  immediately 
a  pure  white  sublimate  near  the  assay,  but  no  color  to  the 
flame.  On  continued  blowing  this  sublimate  moved  farther 
out,  assuming  a  color  which  varied  from  greenish  to  brownish 
yellow,  for  the  most  part  lemon  yellow,  while  the  assay 
changed  to  a  pure  silver  bead.  On  examining  the  coating 
more  minutely  with  a  lens  it  was  seen  to  have  a  peculiar 
smooth  appearance,  as  if  it  had  fused  on  the  surface  of  the 
charcoal,  while  scattered  about  nearer  the  assay  were  numerous 
small  transparent  to  milk-white  globules,  along  with  minute 
globules  of  silver.  These  tests  led  to  the  suspicion  that  the 
mineral  might  possibly  contain  germanium,  and  a  comparative 
test,  made  with  argyrodite  on  charcoal,  gave  exactly  the  same 
results.  It  is  to  be  noted  here  that  while  Richter  *  describes 
very  minutely  the  reactions  which  argyrodite  gives  on  char- 
coal he  does  not  mention  the  smooth  surface  of  the  coating 
or  the  formation  of  the  fused  globules  which  form  so  char- 
acteristic and  useful  a  test  for  the  identification  of  germanium. 
In  order  to  prove  beyond  all  doubt  the  identity  of  the  element 
thus  indicated  with  germanium  the  properties  of  the  element 

*  Quoted  by  Weisbach,  Jahrb.  f .  Min.,  1886,  ii,  p.  67. 


200  ON  ARGYRODITE  AND  ITS 

as  given  by  Winkler  *  were  studied  and  a  series  of  careful 
qualitative  tests  were  made  together  with  the  formation  of 
most  of  the  important  compounds  mentioned  by  him.  Thus 
a  sulpho-salt,  soluble  in  alkaline  solutions  like  those  of  the 
tin,  arsenic,  and  antimony  group,  was  prepared,  from  which 
solution  the  addition  of  acid,  especially  in  large  excess, 
precipitated  a  white  sulphide.  On  heating  some  of  this 
sulphide  in  a  tube  through  which  a  current  of  hydrogen  was 
passed,  small  glittering  scales  of  GeS,  in  luster  resembling 
hematite,  were  formed  just  beyond  the  ignited  material. 
These  on  examination  with  the  microscope  in  transmitted 
light  were  found  to  be  dark  brown  in  color.  Although  not 
mentioned  by  Weisbach  f  it  was  noted  that  these  were  strongly 
pleochroic,  the  direction  of  greatest  absorption  being  at  right 
angles  to  the  longest  axis  of  the  plates.  By  continued  and 
higher  heating  a  still  further  reduction  took  place  and  metallic 
germanium  was  deposited  as  a  crystalline  sublimate  on  the 
walls  of  the  tube.  Microscopic  examination  showed  this 
sublimate  to  consist  of  small  gray-white  octahedral  crystals  of 
magnificent  metallic  luster.  They  were  found  to  be  insoluble 
in  hydrochloric  acid  but  were  readily  dissolved  by  aqua  regia. 
These  results  agree  exactly  with  those  given  by  Winkler, 
and  the  identity  was  still  further  confirmed  by  the  entire 
behavior  of  the  element  and  by  other  results  which  will  be 
given  in  the  course  of  this  article. 

The  physical  properties  of  this  new  mineral  are  as  follows : 
Crystallization  isometric.  Among  the  specimens  furnished  by 
Mr.  Canfield  were  two  which  were  well  crystallized.  One  of 
these  consisted  of  a  group  of  unmistakable  octahedral  crystals, 
averaging  about  7  mm.  in  axial  diameter,  but  which  were  too 
rough  for  measurement  on  the  goniometer.  Their  edges  were 
sometimes  truncated  by  the  dodecahedron,  while  some  were 
twinned  about  an  octahedral  face.  The  other  specimen  con- 
tained equally  large  but  less  isolated  crystals,  the  luster  of 
whose  faces  was  good  and  one  of  the  crystals,  showing  the 

*  Journ.  f.  prakt.  Chern.,  xxxiv,  1886,  p.  177. 
t  Quoted  by  Wiukler,  loc.  cit.,  p.  215. 


OCCURRENCE   IN  BOLIVIA.  201 

four  upper  faces  of  an  octahedron,  with  edges  truncated  by 
the  dodecahedron  was  measured  on  the  reflecting  goniometer 
as  follows: 

111  A  Til  =70°  0' 
Til  A  III  =70°  29' 
TT1  A  1T1  =  70°  14'  111  A  TT1  =  108°  57' 

1T1  A  111  =  70°    8'  1T1  A  Tl  1 .  =  109°    3' 

Calculated    70°  32'  Calculated    109°  28' 

The  reflections  of  the  signal  were  moderately  good  and 
considering  a  slight  rounding  of  the  faces  the  measurements 
agree  as  closely  with  those  of  the  octahedron  as  could  be 
expected.  The  dodecahedral  faces  were  too  uneven  to  yield 
a  distinct  reflection.  These  crystals  were  tested  and  found 
to  give  the  characteristic  reactions  for  germanium.  The 
fracture  is  irregular  to  small  conchoidal.  Extremely  brittle. 
Hardness  about  2.5.  The  specific  gravity  of  two  distinct, 
massive  fragments,  weighing  about  five  and  six  grams  each, 
carefully  taken  on  a  chemical  balance  after  boiling  in  distilled 
water,  was  found  to  be  6.2662  and  6.2657  respectively,  the  tem- 
perature being  25°  C.  The  specific  gravity  of  the  fragment 
containing  the  crystal  that  was  measured  and  weighing  over 
22  grams  was  found  to  be  6.270.  The  luster  is  brilliant  me- 
tallic. The  color  black  with  a  bluish  to  purplish  tone.  The 
streak  is  grayish  black,  somewhat  shiny.  The  chief  pyrognostic 
properties  have  already  been  given.  In  addition,  the  fusibility 
at  about  1J  to  2  should  be  noted.  The  fused  transparent 
globules  which  were  observed  on  charcoal  are  probably  GeO2. 
Some  of  the  oxide  separated  from  the  quantitative  analysis 
was  tested  on  charcoal  as  follows :  In  the  oxidizing  flame  it 
fused  with  bubbling  to  a  transparent,  glassy  globule,  giving 
no  coating.  By  continued  heating  in  the  reducing  flame  it 
darkened  and  gave  slowly  a  pure  white  sublimate.  The 
yellow  coating  obtained  on  charcoal  from  the  mineral  was 
probably  a  mixture  of  oxide  and  sulphide  of  germanium. 
The  fused  globules,  which  were  observed  near  the  assay  in 
the  closed  tube  are  GeS2  or  possibly  some  oxysulphide. 


202  ON  ARGYRODITE  AND  ITS 

Argyrodite  from  Freiberg,  when  tested  in  the  closed  tube, 
gives  at  first  a  black  sublimate,  which,  as  stated  by  Richter,* 
looks  exactly  like  mercuric  sulphide  and  undoubtedly  is  that 
substance.  On  intense  heating  before  the  blowpipe  there 
formed  farthest  up  on  the  tube  a  sublimate  of  sulphur,  next 
followed  the  black  ring  of  mercuric  sulphide,  neither  of  which 
increased  perceptibly  by  continued  heating,  while  nearest  the 
assay  the  nearly  colorless  globules  of  GeS2  were  deposited. 
On  breaking  off  the  lower  end  of  the  tube,  driving  off  the 
sulphur  and  mercuric  sulphide  by  gentle  heat  and  then 
roasting  the  globules  in  a  current  of  air,  SO2  was  given  off 
while  the  germanium  oxide  collected  into  a  fused  mass  but 
was  not  volatilized.  Regarding  the  association  of  canfieldite 
with  other  minerals,  all  that  can  be  said  is  that  the  specimens 
are  remarkably  pure,  only  slight  quantities  of  pyrite,  sphaler- 
ite and  kaolin  being  attached  to  them. 

It  having  been  shown  that  the  mineral  was  essentially  a 
sulpho-salt  of  germanium  and  silver,  the  following  method 
was  adopted  for  analysis.  A  weighed  quantity,  about  two 
grams,  was  oxidized  by  concentrated  nitric  acid,  the  operation 
requiring  from  one  to  two  hours  on  the  water  bath.  After 
the  oxidation  was  complete  the  excess  of  nitric  acid  was 
removed  by  evaporation.  The  residue  was  then  dissolved  in 
warm  water  slightly  acidified  with  nitric  acid,  and  after  filter- 
ing off  a  slight  trace  of  insoluble  residue  the  silver  was  pre- 
cipitated by  hydrochloric  acid,  filtered,  and  weighed.  In  the 
filtrate  the  sulphur  was  precipitated  as  barium  sulphate, 
which  was  purified  by  fusion  with  sodium  carbonate,  repre- 
cipitated  and  weighed.  For  the  determination  of  germanium 
another  portion  of  two  grams  was  oxidized  by  nitric  acid  with 
the  addition  of  a  little  sulphuric  acid.  After  removal  of  the 
large  excess  of  nitric  acid  by  evaporation,  the  residue  was 
dissolved  in  warm  water,  with  addition  of  some  nitric  acid 
if  necessary,  the  silver  precipitated  with  ammonium  thio- 
cyanate  and  removed  by  filtration.  The  filtrate  contained  the 
germanium  together  with  no  acid  which  forms  with  it  a 
*  Quoted  by  Weisbach  and  Winkler. 


OCCURRENCE  IN  BOLIVIA.  203 

volatile  compound.  It  was  evaporated  in  a  platinum  dish, 
the  nitric  acid  present  serving  to  completely  destroy  the 
ammonium  thiocyanate,  and  the  excess  of  sulphuric  acid  was 
finally  driven  off  by  heating.  The  residue  thus  obtained  was 
covered  with  a  little  strong  ammonia  into  which  hydrogen 
sulphide  was  conducted.  Under  this  treatment  the  ger- 
manium oxide  dissolved,  while  all  heavy  metals,  except  those 
which  form  sulpho-salts  soluble  in  ammonium  sulphide,  were 
left  undissolved.  In  this  particular  case  a  very  small  quan- 
tity of  a  black  sulphide  remained ;  it  was  filtered  off,  ignited 
and  weighed.  It  is  assumed  to  be  a  mixture  of  zinc  and  iron 
oxides,  resulting  probably  from  admixed  sphalerite  and  pyrite. 
The  filtrate  containing  the  germanium  was  collected  in  a 
weighed  platinum  crucible  and  evaporated  on  the  water  bath. 
The  residue  was  oxidized  by  strong  nitric  acid,  the  excess  of 
which  was  removed  by  evaporation.  The  crucible,  placed 
inside  a  porcelain  one,  was  then  ignited,  gently  at  first,  finally 
to  the  full  extent  of  a  ring  burner,  then  weighed,  and  the 
germanium  determined  as  GeO2.  On  further  ignition  the 
weight  was  found  to  be  constant,  nor  did  it  change  by  heat- 
ing to  full  redness.  When  heated  in  a  current  of  ammonia 
and  air,  to  remove  sulphuric  acid,  the  weight  diminished  very 
little;  thus  in  one  experiment  it  fell  from  0.1535  to  0.1525 
grams,  showing  that  a  gentle  ignition  is  sufficient  to  practically 
expel  all  of  the  sulphuric  acid.  By  heating  to  a  bright  red- 
ness in  a  current  of  ammonia  and  air  the  germanium  oxide 
suffered  reduction  to  the  metallic  state.  To  show  that  the 
germanium  oxide  was  pure  and  especially  to  prove  the  ab- 
sence of  arsenic  and  antimony  the  following  tests  that  were 
made  may  be  mentioned.  Rather  large  quantities  of  the 
mineral,  when  roasted  in  the  open  tube  gave  no  sublimate. 
An  acid  solution  of  the  oxide  gave  upon  addition  of  hydro- 
gen sulphide  a  white  precipitate,  which  when  collected  on  a 
filter  showed  only  a  pale  tinge  of  yellow.  Also  the  oxide 
obtained  in  the  analysis  when  dissolved  and  brought  into  a 
Marsh  apparatus  gave  only  a  most  minute  and  unweighable 
blackening  on  the  walls  of  the  tube,  which  on  ignition  in  the 


204  ON  ARGYRODITE  AND  ITS 

air  changed  to  a  scarcely  perceptible  white  oxide  resembling 
antimony.  As  the  mineral  dissolves  completely  in  nitric  acid 
tin  cannot  be  present.  These  results  therefore  showed  that 
the  germanium  was  satisfactorily  pure.  Another  method  of 
analysis  in  which  everything  was  determined  in  one  portion 
is  as  follows :  Solution  of  the  mineral  in  nitric  acid,  precipi- 
tation of  the  silver  with  hydrochloric  acid,  of  the  sulphur 
with  barium  nitrate,  removal  of  the  excess  of  chlorine  and 
barium  in  one  operation  with  silver  nitrate  and  sulphuric 
acid,  final  removal  of  the  silver  by  ammonium  thiocyanate 
and  determination  of  the  germanium  in  the  filtrate  as  above. 
The  result  of  the  analysis  gave  the  following  figures : 

Average.     Deducting  Theory  for 
impurities.    Ag8GeS6. 


s 

17.03 

17.04 

.  .  . 

17.04 

17.10 

17.06 

Ge 

6.51 

6.52 

6.61 

6.55 

6.57 

6.42 

Ag 

76.01 

76.09 

76.05 

76.33 

76.52 

Fe  Zn 

014 

016 

010 

013 

Insol. 

0.29 

0.29 

.  .  . 

.  .  . 

100.06      100.00      100.00 

The  formula  of  the  mineral  is  evidently  Ag8GeS6  or  4Ag2S  . 
GeS2.  The  agreement  of  the  analysis  with  the  theory,  as  will 
be  noticed,  is  reasonably  close. 

Winkler  made  the  following  analysis  of  the  Freiberg  argy- 
rodite,  from  which  he  derived  the  formula  Ag6GeS5  or  3Ag2S  . 
GeS2. 

Analysis  by  Theory  for  Theory  for  Atomic 

Winkler.  Ag6Ge5S5.  Ag8GeS6.  weights. 

S  17.13  18.21  17.06            32 

Ge  6.93  8.23  6.42            72.32 

Ag  74.72  73.56  76.52          107.7 

Hg  0.31 

Fe  0.66 

Zn  0.22  _._1_1  _^_^ 

99.97  100.00  100.00 

It  will  be  noticed  that  Winkler 's  analysis  agrees  much 
more  closely  with  the  theory  for  Ag8GeS6,  especially  in  re- 
spect to  the  sulphur  and  germanium,  than  with  the  formula 


OCCURRENCE  IN  BOLIVIA.  205 

advanced  by  him.  It  seems  probable,  therefore,  that  the  two 
minerals  have  the  same  chemical  composition,  but  since  Weis- 
bach  has  shown  that  argyrodite  is  monoclinic  and  since  can- 
fieldite  is  isometric,  they  cannot  be  identical.* 

In  order  to  investigate  this  point  more  closely  it  seemed 
desirable  to  make  a  new  analysis  of  argyrodite  by  the  same 
methods  which  had  been  used  for  canfieldite.  The  material 
was  very  carefully  selected  from  an  excellent  specimen  of 
the  Freiberg  argyrodite  in  the  collection  of  Professor  Brush. 
The  specific  gravity  was  determined  in  two  ways.  Some 
larger  fragments,  weighing  about  two  grams,  gave  on  the 
chemical  balance  in  distilled  water  6.149  and  the  smaller  ones 
gave  by  use  of  the  pycnometer  6.162.  These  results,  though 
somewhat  higher  than  those  given  by  W inkier  and  Weisbach, 
which  were  6.085-6.111,  are  still  considerably  lower  than  the 
specific  gravity  of  canfieldite.  The  results  of  the  analysis 
are  as  follows: 

Average. 

S 16.97  .  .  .  16.97 

Ge 6.67  6.62  6.64 

Ag 75.57  75.53  75.55 

Hg 0.34  .  .  .  0.34 

Fe,  Zn    .  .  .     0.24  .  .  .  0.24 

99.74 

It  will  be  seen  that  this  analysis  agrees  remarkably  well 
with  that  of  Winkler,  the  only  essential  difference  being  that 
the  silver  is  somewhat  higher  and  the  iron  and  zinc  are  lower. 
This  suggests  that  these  latter  are  impurities,  resulting  from 
the  presence  of  a  slight  admixture  of  pyrite  and  sphalerite, 
both  of  which  are  associated  with  the  mineral.  In  regard  to 
the  mercury,  since  this  element  has  never  been  known  to 
occur  otherwise  at  Freiberg,  it  is  probable  that  it  replaces 
silver.  If  we  now  recalculate  these  analyses,  excluding  the 
iron  and  zinc  with  sufficient  sulphur  to  form  pyrite  and 

*  Compare  note  at  the  beginning  of  this  article,  page  198. 


206  ON  ARGYRODITE  FROM  BOLIVIA. 

sphalerite,  and  .replacing  the   mercury  by  its  equivalent  in 
silver,  we  obtain  the  following: 

r.     «  ij-*  Argyrodite,  Argyrodite,  Theory  for 

Canfleldite.  winkler.  Author.  Ag8GeS6. 

17.10  16.56  16.83  17.06 

6.57  7.05  6.69  6.42 

76.33  76.39  76.48  76.52 

100.00  100.00  100.00  100.00 

From  the  consideration  of  these  results  there  can  be  no 
doubt  that  canfieldite  and  argyrodite  have  the  same  chemical 
composition,  which  is  Ag8GeS6.  It  is  evident  therefore  that 
we  have  here  a  case  of  dimorphism,  for  both  the  crystalline 
forms  and  the  specific  gravities  indicate  that  the  minerals 
are  distinct. 


ON  THE  CHEMICAL  COMPOSITION  OF  STAURO- 
LITE,  AND  THE  REGULAR  ARRANGEMENT 
OF  ITS  CARBONACEOUS  INCLUSIONS. 

BY  S.  L.  PENEIELD  AND  J.   H.  PKATT. 
(From  Amer.  Jour.  Sci.,  1894,  vol.  47,  pp.  81-89.) 

Historical.  —  In  the  early  analyses  of  staurolite,  especially 
those  of  Jaeobson  *  and  Rammelsberg,f  a  great  variation  was 
found  in  the  chemical  composition,  especially  in  the  amounts 
of  silica,  which  varied  all  the  way  from  27  to  50  per  cent. 
The  iron  oxide,  moreover,  was  regarded  by  some  investigators 
as  ferric,  by  others  as  ferrous,  while  still  others  considered 
that  it  existed  in  both  states  of  oxidation. 

In  1865  Lechartier  J  observed  that  pulverized  staurolite 
from  Brittany  and  Bolivia,  when  examined  with  the  micro- 
scope, showed  both  brown  and  colorless  grains.  On  treat- 
ment with  hydrofluoric  acid,  it  was  found  that  the  colorless 
ones  dissolved,  while  the  staurolite  was  very  slightly  at- 
tacked. Furthermore,  material  purified  by  this  treatment 
was  found  to  be  nearly  uniform  in  specific  gravity  and  gave 
amounts  of  SiO2  varying  from  28-29  per  cent,  agreeing  with 
the  purest  staurolite  from  St.  Gothard.  He  also  proved  that 
water  was  an  essential  constituent  of  the  mineral. 

In  1872,  Von  Lasaulx  §  showed,  from  a  microscopic  exam- 
ination of  staurolite  from  various  localities,  that  all  crystals 
are  more  or  less  impure  from  mechanical  admixtures,  espe- 
cially of  quartz,  while  garnet,  cyanite,  magnetite  and  mica 
were  also  observed.  These  inclusions  of  quartz,  amounting 
sometimes  to  30-40  per  cent  of  the  total  weight  of  the  crys- 

*  Fogg.  Ann.,  Ixii,  p.  419,  1844,  and  Ixviii,  p.  414, 1846. 

t  Fogg.  Ann.,  cxiii,  p.  599,  1861.        ,      J  Bull.  Soc.  Chimique,  iii,  p.  378. 

§  Min.  Mittheilung,  1872,  p.  173. 


208        CHEMICAL   COMPOSITION  OF  STAUROLITE. 

tals,  account  for  the  great  variation  of  the  silica  percentages 
in  the  older  analyses. 

In  1873  Rammelsberg  *  re-examined  the  exceptionally  pure 
staurolite  from  St.  Gothard  and  also  the  impure  material  from 
Pitkaranta  and  Brittany,  in  which  he  had  previously  found 
over  50  per  cent  of  silica.  After  purifying  these  latter  by 
treatment  with  hydrofluoric  acid,  only  from  29  to  30  per  cent 
of  silica  was  found  and  the  analyses  agreed  with  that  of  the 
St.  Gothard  mineral.  From  these  analyses  he  deduced  the 
formula  HaFegAl^SieOs^  the  iron  being  regarded  as  ferrous 
and  replaced  in  part  by  magnesia. 

In  1885  Friedl  f  investigated  carefully  selected  material 
from  St.  Gothard  and  Tramnitzberg  in  Mahren,  which  by 
examination  with  the  microscope  had  been  found  to  be  free 
from  foreign  inclusions.  From  the  results  of  his  analyses 
he  deduced  the  formula  H4Fe6Al24SinO66.  In  the  same  year 
ColoranioJ  analyzed  the  St.  Gothard  staurolite,  which  had 
been  carefully  selected  and  digested  with  hydrofluoric  acid, 
the  formula  deduced  by  him  being  H2Fe2Al12Si5O31. 

It  is  interesting  to  note  the  variations  in  the  proposed 
formulae,  each  investigator  in  turn  finding  a  smaller  amount 
of  silica,  as  shown  below,  where  the  formulae  of  Rammelsberg 
and  Coloranio  have  been  doubled  for  more  ready  comparison. 

Kammelsberg H4Fe6Al24Si12068 

Friedl     H4Fe6Al24Siu066 

Coloranio     H4Fe4Al24Si1()062 

From  a  consideration  of  the  analyses  of  Friedl  and  Coloranio, 
Groth  §  concludes  that  staurolite  has  a  still  simpler  formula, 
and  suggests  a  basic  orthosilicate  (AlO)4(AlOH)Fe(SiO4)2. 

Selection  and  preparation  of  material  for  analysis.  —  In 
the  present  investigation,  material  of  exceptional  purity  was 
selected  from  the  four  following  localities:  St.  Gothard, 

*  Zeitschr.  Deutsch.  geol.  Gesell.,  xxv,  p.  53. 

t  Zeitschr.  Kryst,  x,  p.  366. 

J  Bull.  Soc.  Chimique,  xliv,  p.  427. 

§  Tabellarische  Uebersicht  der  Mineralien,  1889,  p.  104. 


CHEMICAL   COMPOSITION  OF  STAUROLITE.       209 

Switzerland ;  Windham,  Maine ;  Lisbon,  New  Hampshire,  and 
near  Burnsville,  North  Carolina.  The  material  from  the 
first  of  these  is  too  well  known  to  need  special  description. 
Some  crystals  from  the  Brush  collection  were  available.  At 
Windham,  Maine,  it  occurs  in  crystals  measuring  up  to  25 
mm.  in  diameter,  imbedded  in  mica  schist,  as  represented  by 
an  excellent  suite  of  specimens  in  the  Brush  collection.  This 
has  never  been  previously  analyzed.  The  material  from 
Sugar  Hill  in  Lisbon,  N.  H.,  was  collected  in  the  summer  of 
1893  by  Professor  Brush.  As  observed  by  him,  extensive 
ledges  of  gray  staurolitic  mica  schist  occur,  extending  several 
miles  north  from  Pearl  Lake,  better  known  as  Mink  Pond, 
and  including  the  ledges  on  Garnet  Hill  and  Co  wen  Hill.  In 
the  ledges  on  Cowen  Hill  unusually  large  and  fresh  crystals 
are  found  measuring  up  to  115  mm.  long  by  40  mm.  broad. 
Thin  sections  of  these  crystals  revealed  the  fact  that  they  are 
remarkably  free  from  inclusions  of  quartz  and  garnet,  which 
are  so  common  in  staurolite,  but  they  contain  carbonaceous 
material  arranged  in  certain  definite  planes,  as  described  later. 
The  staurolite  from  near  Burnsville  was  collected  by  the 
writers  in  the  summer  of  1892,  while  engaged  in  work  for  the 
North  Carolina  Geological  Survey.  It  was  found  at  and  near 
a  prospect  pit  on  the  property  of  Mr.  D.  M.  Hampton,  which 
had  been  dug  in  exploiting  for  iron  ore.  The  associated 
minerals  are  magnetite,  menaccanite,  and  corundum.  The 
staurolite  occurs  in  crystalline  aggregates,  often  intimately 
associated  with  the  iron  ores. 

In  the  preparation  of  material  for  analysis  the  carefully 
selected  crystals  were  pulverized  and  sifted  to  a  uniform  grain. 
In  the  case  of  the  North  Carolina  mineral  the  magnetite  and 
menaccanite  were  removed  by  means  of  an  electro-magnet. 
In  order  to  separate  a  powder  of  uniform  specific  gravity 
the  use  of  fused  silver  nitrate,  which  may  be  diluted  with 
potassium  nitrate,  was  resorted  to,  as  recommended  by  J.  W. 
Retgers.*  It  was  found  convenient  to  use  a  double-walled, 
cylindrical  copper  air  bath,  shown  in  section  in  the  accom- 

*  Jahrb.  fur  Min.,  1889,  ii,  p.  190. 
14 


210        CHEMICAL   COMPOSITION  OF  STAUROLITE. 


panying  figure.  The  outer  cylinder  a  stands  on  legs  which 
are  not  represented.  The  inner  bath  is  supported  by  brackets, 
£,  and  is  provided  with  several  perforated 
discs  near  the  bottom,  which  serve  to 
disseminate  the  heat  of  the  lamp.  The 
well  A  holds  a  test  tube  containing  the 
silver  nitrate,  which  can  readily  be  kept 
in  a  state  of  fusion  and  at  a  constant 
temperature  for  any  desired  length  of 
time ;  this  latter  condition  being  very  es- 
sential in  order  to  avoid  circulating  cur- 
rents. The  fusing  point  of  silver  nitrate 
is  198°  C.,  but  the  temperature  which 
was  found  most  convenient  for  work  was 
about  250°  C.  The  specific  gravity  of 
fused  AgNO8  is  about  4.1  which  may  be 
lowered  by  addition  of  KNO3.  The 
fused  salt  is  a  clear  mobile  liquid,  through  which  the  particles 
of  mineral  move  freely,  and  separations  can  be  made  in  this 
as  accurately  as  in  any  of  the  heavy  solutions.  On  cooling, 
the  fusion  solidifies  to  a  cake  with  the  heavier  and  lighter 
portions  at  the  bottom  and  top,  respectively.  The  test  tube 
readily  breaks  away  from  the  fused  mass,  the  cake  can  be  cut 
in  two  and  the  minerals  separated  by  dissolving  the  nitrates 
in  water.  The  latter  can  be  reclaimed  by  evaporating  the 
solutions  to  dryness  on  a  water  bath  and  finally  fusing.  By 
eliminating  the  heavier  and  lighter  portions  and  repeating 
the  separation,  remarkably  pure  products  were  obtained,  of 
nearly  uniform  specific  gravity.  The  manipulations  are  very 
simple  and  the  results  extremely  satisfactory.  A  preliminary 
experiment  that  was  made  showed  that  staurolite  does  not 
suffer  any  decomposition  or  loss  in  weight  when  exposed  to 
a  temperature  of  250°  C.  The  separated  material,  when 
examined  with  the  microscope,  was  found  to  be  homogeneous 
and  very  free  from  visible  inclusions. 

Method  of  analysis.  —  The  silica  and  bases  were  determined 
by  well  known  methods.     The  evaporations  were  carried  on 


CHEMICAL   COMPOSITION  OF  STAUROLITE.        211 

in  platinum,  the  purity  of  the  silica  tested  by  evaporation  with 
hydrofluoric  acid  and  account  taken  of  the  small  quantity 
of  silica  carried  along  and  weighed  with  the  sesquioxides. 
Especial  care  was  taken  in  the  determination  of  ferrous  and 
ferric  iron.  The  very  finely  pulverized  mineral  was  treated  in 
a  small  platinum  bottle  with  a  mixture  of  strong  hydrofluoric 
and  sulphuric  acids  and  boiled  vigorously  for  about  twenty 
minutes,  the  neck  of  the  bottle  being  covered  by  a  cone  of 
platinum  foil.  The  contents  of  the  bottle  were  then  diluted 
with  cold  boiled  water,  washed  into  a  casserole  and  titrated 
with  potassium  permanganate.  Preliminary  experiments  were 
made  by  treating  known  weights  of  ferrous  sulphate  in  the 
same  manner  and  it  was  found  that  no  appreciable  oxidation 
from  the  air  took  place.  As  the  staurolite  is  very  slowly 
attacked  by  hydrofluoric  acid  only  a  portion  in  each  experi- 
ment went  into  solution.  After  titration,  the  insoluble  portion 
was  filtered  off  and  the  filtrate  evaporated  in  a  platinum  dish 
till  all  the  hydrofluoric  acid  was  expelled.  After  diluting, 
the  iron  was  reduced  by  hydrogen  sulphide,  the  excess  of  the 
latter  removed  by  boiling  and  the  total  iron  determined  by 
means  of  potassium  permanganate.  The  determinations  give 
the  ratio  of  ferrous  to  ferric  iron  in  that  portion  which  had 
been  dissolved  by  the  hydrofluoric  acid,  and  the  total  iron  in 
the  mineral  having  been  previously  found  in  the  portion 
used  for  silica  and  bases,  the  percentages  of  ferrous  and  ferric 
iron  are  readily  calculated.  Direct  determinations  of  water 
were  made  in  all  cases,  as  loss  by  ignition  would  naturally 
give  too  low  results,  owing  to  the  oxidation  of  the  ferrous 
iron. 

Analytical  results.  —  The  results  of  the  analyses  are  given 
below,  together  with  the  specific  gravity  determinations  which 
were  made  very  carefully  by  means  of  the  pycnometer. 


212        CHEMICAL   COMPOSITION  OF  STAUROLITE. 


St. 

Gothard,  Switzerland. 

Specific  gravity  = 

3.748. 

i.                  n. 

Si02 

27.80            27.65 

A1203 

53.23            53.35 

Fe208 

2.83              2.83 

FeO 

11.21            11.20 

MnO 

0.63              0.44 

MgO 

1.77              1.85 

H20 

2.19 

Average. 

27.73 
53.29 

2.83 

11.21 

0.53 

1.81 

2.19 

99^59 


Windham,  Maine. 
Specific  gravity  =  3.728. 


Si02 

A1203 

Fe203 

FeO 

MnO 

MgO 

H20 


i. 

27.81 

54.44 

2.81 

10.52 

0.59 

1.83 

2.24 


n. 

27.88 
54.51 

2.90 

10.85 

0.62 

1.87 


III. 

Average. 

. 

27.84 

54.36 

54.46 

2.80 

2.83 

10.44 

10.60 

0.56 

0.59 

•  .  • 

1.85 

.  .  . 

2.24 

100.41 


Lisbon,  New  Hampshire. 


Specific  gravity  =  3.775. 
Si02  .  .  .  . 
A1203  .  .  .  . 
Fe203 

FeO 

MgO     

H20 


27.81 

54.09 

2.76 

12.48 

1.92 

1.70 


100.76 


Burnsville,  North  Carolina. 

Specific  gravity  = 

=  3.773. 

i. 

ii. 

in. 

IV. 

Si02 

27.80 

27.65 

27.59 

27.77 

A1203 

53.09 

53.30 

.  .  . 

53.27 

Fe203 

4.81 

4.81 

4.83 

4.85 

FeO 

9.70 

9.68 

9.74 

9.79 

MnO 

0.27 

0.38 

0.33 

0.36 

MgO 

2.64 

2.65 

2.70 

.  .  . 

H20 

1.99 

1.96 

.  .  • 

.  .  . 

Average. 

27.70 

53.22 

4.82 

9.72 

0.34 

2.66 

1.97 

TOO43 


CHEMICAL   COMPOSITION  OF  STAUROLITE.       213 

For  a  better  comparison  of  the  results  the  average  analyses 
are  given  below,  after  recalculating  Fe2O3  as  A12O3,  MnO  and 
MgO  as  FeO  and  bringing  the  whole  to  one  hundred  per  cent. 

St.  Gothard,  Switz.       Windham,  Me.     Lisbon,  N.  H.    Burnsville,  N.  C. 


Si02 

27.70 

27.60 

27.44 

27.47 

A1208 

55.04 

55.75 

55.16 

55.83 

FeO 

15.07 

14.43 

15.72 

14.74 

HaO 

2.19 

2.22 

1.68 

1.96 

100.00 

100.00 

100.00 

100.00 

The  ratios  in  these  analyses  are  as  follows : 

SiO2    :  A12O3  :    FeO    :    H20 

St.  Gothard        0.460  :  0.540  :  0.209  :  0.121  =  2.12  :  2.50  :  0.967  :  0.560 
Windham  0.460  :  0.546  :  0.200  :  0.122  =  2.11  :  2.50  :  0.915  :  0.557 

Lisbon  0.457  :  0.540  :  0.218  :  0.093  =  2.11  :  2.50  :  1.01    :  0.430 

Burnsville          0.458  :  0.547  :  0.205  :  0.109  =  2.07  :  2.50 :  0.934  :  0.497 

The  above  ratios  approximate  closely  to  2  :  2.5  :  1  :  0.5 
which  would  give  the  formula  HAl5FeSi2Oi3,  in  which  the 
aluminium  is  partly  replaced  by  ferric  iron  and  the  ferrous 
iron  by  magnesium  and  manganese.  This  is,  moreover,  the 
formula  suggested  by  Groth,  and,  as  previously  stated,  may 
be  written  as  a  basic  orthosilicate,  (AlO)4(AlOH)Fe(SiO4)2 
or  equally  well,  (AlO)4Al(FeOH)(SiO4)2.  The  percentage 
composition  required  by  the  formula  is  the  following : 

Si02 26.32 

A1203 55.92 

FeO 15.79 

H20 1.97 

100.00 

From  a  comparison  of  the  ratios,  or  of  the  analyses  as  re- 
duced, with  the  theory,  it  will  be  observed  that  the  silica  is 
uniformly  a  trifle  high,  amounting  to  something  over  one  per 
cent.  This  cannot  be  referred  to  an  analytical  error,  as  the 
distilled  water  and  reagents  were  pure,  and  platinum  vessels 
were  used  for  the  evaporations.  It  was  not  derived  from  the 
agate  mortar  in  which  the  mineral  was  ground,  for  in  the 


214       CHEMICAL   COMPOSITION  OF  STAUROLITE. 

analysis  of  the  mineral  from  Lisbon  a  steel  mortar  was  used, 
the  powder  being  afterwards  purified  by  treatment  with  hydro- 
chloric acid.  From  the  careful  selection  of  nearly  pure  min- 
eral to  start  with,  and  the  special  precautions  that  were  taken 
to  eliminate  all  heavier  and  lighter  portions  by  the  specific 
gravity  separation,  it  was  not  expected  that  the  staurolite 
grains  would  still  contain  inclusions  of  quartz,  nor  were  they 
visible  in  the  fragments,  when  examined  with  the  microscope ; 
from  the  results  of  the  analyses,  however,  it  is  evident  that 
they  were  not  wholly  eliminated.  To  test  this  point  more 
carefully,  the  following  experiments  were  made  on  some  of 
the  finely  powdered  minerals  left  over  from  the  regular 
analyses.  After  digesting  with  cold,  strong  hydrofluoric 
acid  for  twelve  hours  and  washing,  silica  determinations  were 
made,  which  are  given  below,  along  with  the  determinations 
from  the  previous  analyses. 

St.  Gothard.        Windham,  Me.       Lisbon,  N.  H. 

Si02  after  treatment  with  HF,        27.52  27.36  27.15 

Si02  from  regular  analyses  27.73  27.84  27.81 

It  will  be  observed  that  hydrofluoric  acid  has  removed  some 
silica,  but  still  the  percentages  are  higher  than  the  theory. 
We  should  infer,  therefore,  that  quartz  is  an  impurity  in  the 
mineral  and  that  it  is  present  as  very  minute  inclusions.  If, 
for  example,  the  inclusions  are  as  fine  or  finer  than  the  acicu- 
lar  crystals  of  rutile  in  quartz,  they  could  not  be  removed 
by  a  specific  gravity  separation,  nor,  being  enclosed  in  the 
staurolite,  would  they  be  wholly  accessible  to  the  action  of 
hydrofluoric  acid.  That  the  formula  suggested  by  Groth  is 
correct  is  well  established  by  our  analyses  and,  surely,  its 
simplicity  is  one  of  the  strongest  arguments  that  can  be 
advanced  for  its  acceptance. 

On  the  regular  arrangement  of  inclusions  in  staurolite 
crystals.  —  In  examining  orientated  thin  sections  of  crystals 
from  Lisbon,  N.  H.,  it  was  observed  that  they  all  contained 
dark  inclusions,  arranged  in  certain  definite  planes,  resembling 
the  phenomena  so  common  in  andalusite.  That  the  inclu- 


INCLUSIONS  IN  STAUROLITE.  215 

sions  are  carbonaceous  material  was  proved  by  the  fact  that, 
on  separating  the  pulverized  mineral  by  specific  gravity,  the 
dark  portion  was  found  to  be  lighter  than  the  clear  staurolite, 
and  on  igniting  it  in  a  current  of  air,  purified  by  passing 
over  caustic  potash,  carbon  dioxide  was  abundantly  evolved. 
These  inclusions  can  only  be  clearly  seen  in  plates  ground 
sufficiently  thin  to  be  transparent  and  can  best  be  studied  in 
basal  sections. 


FIGURE  1.  FIGURE  2.  FIGURE  3.  FIGURE  4. 

Figures  1  to  4  represent  the  arrangement  of  the  inclusions 
in  plates  cut  from  a  simple  prismatic  crystal  50  mm.  in  length 
by  11  mm.  broad  from  which  eleven  basal  sections  were  cut. 
Near  the  ends  the  impurities  are  arranged  as  in  Figure  1 ;  at  the 
middle  the  appearance  is  that  of  a  simple  dark  cross,  Figure 
4;  while  intermediate  sections  show  the  rhomb  diminishing 
in  size  as  the  sections  approach  the  middle  of  the  crystal, 
Figures  2  and  3.  A  number  of  crystals  were  cut  showing 
these  same  phenomena  and  the  symmetrical  arrangement  of 
the  rhomb  and  cross  was  always  well  marked.  The  central 
portions  a  and  the  outer  ones  &,  up  to  the  very  edges  of  the 
section,  are  remarkably  pure  staurolite.  The  dark  bars  run- 
ning parallel  to  the  macro-axis  broaden  as  they  approach  the 
outer  angle  of  the  section  and  are  more  regular  and  better 
defined  than  the  brachy-diagonal  ones.  From  a  series  of 
sections,  then,  it  is  evident  that  each  staurolite  prism  contains 
two  skeleton  or  phantom  pyramids,  P,  outlined  by  carbonaceous 
material,  whose  bases  correspond  to  the  basal  planes  of  the 
staurolite  and  whose  apices  join  at  the  center,  while  from  the 
acute  and  obtuse  pole  edges  of  the  pyramids  the  inclusions 
extend  as  films  or  fins  A  and  B  to  the  vertical  edges  of  the 
prism,  Figure  5,  the  numbers  at  the  side  of  the  figure  indi- 
cating where  sections  should  be  cut  to  give  the  phenomena 


216 


INCLUSIONS  IN  STAUROLITE. 


\ 

iy] 

\ 

R 

3 

\ 

y 

I 

\ 

i 

\ 

I 

\ 

FIGURE  5. 


FIGURE  6. 


corresponding  to  Figures  1  to  4  respectively.  Regularly 
arranged  inclusions  have  previously  been  observed  in  stau- 
rolite,*  but  apparently  they  have  never  been  studied  from  a 
series  of  sections  from  a  single  crystal. 

In  seeking  for  an  explanation  of  these  inclusions,  it  must  be 
borne  in  mind  that  staurolite  is  a  mineral  occurring  essentially 
in  the  crystalline  schists,  which  were  probably  derived  from 
former  mud  or  clay  deposits.  The  crystals  were  formed  by 
metamorphic  agencies,  under  great  pressure,  in  rocks  which 
were  probably  quite  firm  and  solid  while  the  staurolite  was 
forming.  The  crystals,  therefore,  must  have  exerted  great 
force  in  crowding  away  the  surrounding  rock  material  in 
order  to  make  room  for  their  growth,  and  we  must  take  into 
consideration  their  inability  to  exclude  foreign  matter  under 
these  conditions,  as  well  as  their  tendency  to  take  it  up. 
Large  crystals  have  surely  resulted  from  a  growth  about 
smaller  ones  and  the  beginnings  of  the  crystals  under  con- 
sideration were  undoubtedly  at  the  centers,  where  the  apices 
of  the  pyramids,  P,  Figure  5,  join.  In  the  development  of  a 
large  crystal  from  a  small  one  it  is  imagined  that  at  various 

*  C.  T.  Jackson,  Alger's  Phillips  Mineralogy,  1844,  p.  112 ;  Dana's  Min., 
Sixth  edition,  p.  560 ;  S.  Webber,  Proc.  Nat.  Institution  for  the  Promotion  of 
Sci.,  Bull.  2,  p.  197,  1842 ;  A.  Lacroix,  Min.  de  la  France,  1893,  p.  11. 


INCLUSIONS  IN  STAUROLITE.  217 

points  on  the  crystal  faces  the  growth  commences.  The 
addition  of  particles  or  of  crystal  molecules  must  then  advance, 
forcing  foreign  matter  to  one  side  until  the  crystal  surfaces 
are  complete.  The  particles,  however,  which  meet  to  form 
the  edges  of  the  crystals  may  come  together  in  such  a  way 
that  they  cannot  exclude  certain  foreign  materials.  It  would, 
moreover,  seem  reasonable  to  expect  that  the  more  obtuse 
the  angle  at  which  the  faces,  or  the  crystal  molecules  forming 
the  faces,  meet  to  form  an  edge,  the  less  tendency  there  would 
be  to  hold  impurities,  while  the  more  acute  the  edge  the 
greater  this  tendency  would  become.  If  these  conclusions  are 
correct,  then  inclusions  would  be  taken  up  by  the  edges,  and 
being  largely  of  carbonaceous  material,  as  in  the  staurolite 
under  consideration,  the  result  would  be  that,  in  the  develop- 
ment of  a  large  crystal  from  a  smaller  one,  the  inner  prism  I, 
Figure  6,  as  it  enlarged  to  form  II,  III,  IV,  would  leave  a 
dark  deposit  along  the  paths  described  by  its  advancing  edges, 
corresponding  to  the  planes  A,  B  and  P  of  Figure  5.  In 
examining  many  basal  sections  it  has,  moreover,  been  generally 
observed  that  the  bars  running  parallel  to  the  macro-axis, 
representing  the  impurities  taken  up  at  the  acute  edges  of  the 
prism,  are  the  heaviest,  those  parallel  to  the  brachy-axis  are 
the  lightest  and  in  some  sections  practically  fail,  while  the 
outlines  of  the  inner  rhomb,  representing  the  impurities  taken 
up  along  the  edges  of  90°  between  prism  and  base,  are 
intermediate  as  regards  the  quantity  of  included  matter. 
Also  the  inclination  of  the  phantom  pyramid,  P,  Figure  5, 
seems  to  be  wholly  dependent  upon  the  relative  development 
of  the  prism  and  base  during  the  growth  of  the  staurolite 
crystal  and  to  be  in  no  way  connected  with  the  length  of  the 
vertical  axis  as  expressed  by  the  axial  ratio  a  :  b  :  c. 

The  considerations  given  above  seem  sufficient  to  account 
for  the  curious  arrangements  of  the  impurities  in  the  crystals 
under  consideration  and  doubtless  by  a  similar  explanation 
the  impurities  in  some  andalusite  crystals  could  be  accounted 
for. 


ON     THE     CHEMICAL    COMPOSITION    OF    CHON- 
DRODITE,   HUMITE,   AND   CLINOHUMITE. 

BY   S.   L.  PENFIELD  AND  W.  T.   H.  HOWE.* 
(From  Amer.  Jour.  Sci.,  1894,  vol.  47,  pp.  188-206.) 

Introduction.  —  These  minerals,  which  are  regarded  collec- 
tively as  the  humite  group,  have  been  the  subject  of  repeated 
crystallographic  and  chemical  investigation.  For  our  knowl- 
edge of  their  crystallization  we  are  indebted  to  such  careful 
and  accurate  observers  as  Hatty,  Phillips,  G.  Rose,  LeVy, 
Miller,  Hausmann,  Hessenberg,  A.  Scacchi,  vom  Rath,  Nor- 
denskiold,  Kokscharow,  J.  D.  and  E.  S.  Dana,  C.  Klein,  Des 
Cloizeaux  and  Hj.  Sjogren,  whose  names  are  familiar  to  all 
workers  in  crystallography  and  mineralogy.  It  is  not  the 
purpose  of  this  article  to  take  up  the  details  of  the  crystal- 
lization of  these  minerals  nor  to  review  the  progressive  steps 
by  means  of  which  we  have  derived  our  present  knowledge 
of  their  highly  modified  and  complicated  crystalline  structure, 
but  reference  may  be  made  to  the  excellent  historical  sketch 
in  the  recent  edition  of  Dr.  Hintze's  Mineralogy,  page  370. 
In  the  description  of  the  crystals  that  were  examined  during 
the  course  of  our  investigation  we  shall  use  essentially  the 
same  system  of  lettering  and  of  crystal  notation  adopted  by 
A.  Scacchi  f  and  E.  S.  Dana.f 

In  the  humite  group  three  distinct  species  are  at  present 
recognized,  each  characterized  by  the  occurrence  of  certain 
forms  which  are  not  found  on  the  others  and  having  the 
following  axial  relations: 

*  This  article  has  been  somewhat  shortened  by  omitting  both  the  descrip- 
tions of  methods  employed  in  preparing  materials  for  analysis  and  the  dis- 
cussions of  analyses  made  by  other  investigators.  — EDITOR. 

t  Pogg.  Ann.,  Erg.  B.,  iii,  p.  161,  1851. 

t  Mineralogy,  sixth  edition,  p.  535.    Trans.  Conn.  Acad.,  iii,  p.  67. 


CHONDRODITE,   HUMITE,  AND   CLINOHUMITE.       219 

Chondrodite,  Monoclinic  .  .  .  .  a  :  b  :  c  =  1.08630  :  1  :  3.14472;  0  =  90* 

»      Humite,          Orthorhombic  .  .  a  :  6  :  c  —  1.08021  :  1  :  4.40334  ;  ft  =  90  f 

Clinohumite,  Monoclinic     .  .  .  a  :  b  :  c  =  1.08028  :  1  :  5.65883 ;  £  =  90  J 

In  the  above  the  a  axes  are  practically  alike,  while,  as 
shown  by  Scacchi  and  vom  Rath,  a  simple  relation  exists 
between  the  vertical  axes,  that  of  chondrodite  being  |ths  and 
that  of  humite  -Jths  the  length  of  the  clinohumite  axis. 
These  relations  are  shown  in  the  following  table,  to  which 
the  axial  ratio  of  chrysolite,  a  closely  related  mineral,  has 
also  been  added. 

Chondrodite a:    bi^c  —  1.08630  :  1  :  0.62894 

Humite a:    b:  $c  =  1.08021  :  1  :  0.62905 

Clinohumite a:    b:  $e  =  1.08028  :  1  :  0.62876 

Chrysolite     b  :  2a  :     c  =  1.0735    :  1  :  0.6296 

It  is  evident  from  the  above  that  the  first  three  minerals 
form  a  crystallographic  series  and  that  all  of  the  forms  occur- 
ring on  them  could  practically  be  referred  to  one  system  of 
axes,  but  by  so  doing  the  parameter  relations  on  the  vertical 
axis  would  become  exceedingly  complicated.  Chondrodite 
and  clinohumite,  although  their  inclination  0  is  90°,  are 
monoclinic  both  as  regards  the  symmetry  in  the  development 
of  the  faces  and  their  optical  properties,  chondrodite  show- 
ing an  extinction  of  26°-30°  and  clinohumite  7J°-l2l°  from 
the  vertical  axis,  while  humite  in  all  of  its  properties  is 
orthorhombic. 

The  chemical  relations  of  the  minerals  have  never  been 
satisfactorily  determined.  This  is  owing  partly  to  the  fact 
that  it  has  been  difficult  to  obtain  pure  materials  in  sufficient 
quantity  for  analysis,  while  the  analytical  difficulties  in  the 
accurate  determinations  of  silica  and  fluorine  have  not  always 
been  overcome.  Water  in  the  form  of  hydroxyl,  which  is 
an  unfailing  constituent  of  the  minerals,  has  either  been 

*  E.  S.  Dana,  loc.  cit. 

t  A.  Scacchi,  loc.  cit. 

t  Vom  Rath,  Fogg.  Ann.,  Erg.  B.,  v,  p.  373,  1871. 


220  ON  THE   CHEMICAL   COMPOSITION  OF 

overlooked  or  incorrectly  determined.  Scacchi  *  regarded  the 
minerals  as  representing  three  types  of  crystallization  of  one 
and  the  same  chemical  substance,  which  he  designated  as 
humite  type  I,  type  II  and  type  III.  Rammelsbergf  and 
vom  Rath  J  have  suggested  for  the  whole  group  the  formula 
Mg5Si2O9,  with  part  of  the  oxygen  replaced  by  fluorine,  al- 
though they  recognized  that  the  percentages  of  silica  varied 
in  the  different  types.  Wingard  §  also,  from  the  results  of 
his  recent  analyses,  concludes  that  the  three  minerals  have 
the  same  chemical  composition,  expressed  by  the  formula 
Mg19F4(OH)2Si8O38,  while  Hj.  Sjogren,||  largely  from  a  recal- 
culation of  the  older  analyses  and  a  consideration  that  water 
had  been  overlooked  in  them,  derived  a  separate  formula  for 
each  species,  as  follows : 

Clinohumite Mg5[Mg(OH,  F)]2  [SiOJ, 

Humite Mg,[Mg(OH,  F)]2  [Si04]2 

Chondrodite Mg4[Mg(OH,  F)]4  [Si04]3 

S jogren  assumes  that  hydroxyl  is  isomorphous  with  fluorine, 
and  calls  attention  to  the  fact,  already  suggested  by  Rammels- 
berg  and  vom  Rath,  that  the  three  minerals  show  a  variation 
in  their  silica  percentages. 

In  the  present  investigation  we  have  been  able  to  examine 
the  following  materials:  Chondrodite  from  Warwick  and 
Brewster's,  New  York ;  Kafveltorp,  Sweden,  and  Mte.  Somma, 
Italy.  Humite  and  clinohumite  from  Mte.  Somma. 

After  having  definitely  determined  the  crystallographic 
character  of  the  minerals  they  were  pulverized  and  sifted  to  a 
uniform  grain  and  separated  from  the  gangue  and  other 
impurities  by  means  of  the  barium-mercuric-iodide  solution. 
Thanks  to  this  accurate  method  of  separation,  we  have  had  an 
advantage  over  all  previous  investigators  in  being  able  to 

*  Loc.  cit.  t  Mineralchemie,  p.  434, 1875. 

J  Fogg.  Ann.,  cxlrii,  p.  254,  1872. 

§  Zeitschr.  Anal.  Chem.,  xxiv,  p.  344, 1885. 

||  Zeitschr.  Kryst.,  vii,  p.  354, 1883. 


CHONDRODITE,  HUMITE,   AND   CLINOHUMITE.       221 

obtain  an  abundance  of  material  for  the  chemical  analyses. 
Each  product  that  was  obtained  was  nearly  uniform  in  specific 
gravity  and  almost  absolutely  pure,  as  shown  by  examination 
with  the  polarizing  microscope. 

CHONDRODITE  (Humite,  Type  II  of  Scacchi). 

Chondrodite  from  Warwick,  Orange  Co.,  N.  Y.  —  The 
material  that  was  selected  for  analysis  was  obtained  from  a 
specimen  in  the  Brush  collection,  Catalogue  No.  2054.  The 
chondrodite  occurs  as  rounded  grains,  of  a  rich  reddish-brown 
color  imbedded  in  a  white  crystalline  limestone  and  associated 
with  spinel  and  graphite.  The  material  was  very  fresh  and 
showed  occasional  crystal  faces,  but  not  sufficient  for  the 
identification  of  the  mineral.  It  was  selected  at  the  beginning 
of  our  investigation,  as  it  afforded  abundant  material  for 
testing  the  methods  of  the  mechanical  separation  and  the 
chemical  analysis.  The  powder  separated  by  the  heavy  solu- 
tion varied  in  specific  gravity  between  the  limits  8.165  and 
3.235.  It  showed  only  a  trace  of  impurities  when  examined 
with  the  microscope,  probably  of  partly  altered  spinel,  which 
accounts  for  the  small  amount  of  A12O3  shown  by  the  analysis. 
That  the  mineral  is  really  chondrodite  is  proved  by  the 
chemical  analysis,  as  will  be  shown  later,  while  from  the  same 
locality  there  is  in  the  Brush  collection  a  small  specimen, 
Catalogue  No.  2057,  corresponding  exactly  in  color  and 
showing  crystals  that  could  be  measured  and  identified  as 
chondrodite.  These  are  associated  with  an  ash-gray  amphi- 
bole  and  have  evidently  weathered  out  from  limestone. 

Chondrodite  from  the  Tilly  Foster  mine,  Brewster,  Putnam 
Co.,  N.  Y.  —  The  material  for  analysis  was  selected  wholly 
from  isolated  crystals,  which  were  obtained  by  the  present 
writers  at  the  locality.  Each  crystal  was  measured  and  found 
to  possess  characteristic  chondrodite  forms.  The  habits  of 
different  crystals  varied  considerably  but  conformed  in  general 
to  types  figured  by  E.  S.  Dana. 

Chondrodite  from  Kafveltorp,  Sweden.  —  The  material  for 


222 


ON  THE   CHEMICAL   COMPOSITION  OF 


our  investigation  was  obtained  from  a  specimen  in  the  Brush 
collection,  Catalogue  No.  2040.  The  crystals  have  a  yellowish 
brown  color,  are  imbedded  in  sulphides,  and  their  habit  as 
well  as  this  unusual  association  agree  exactly  with  the 
description  given  by  Hj.  Sjb'gren ;  the  accompanying  minerals 
being  chiefly  galena  and  sphalerite  with  a  little  chalcopyrite 
and  amphibole. 

Chondrodite  from  Mte.  Somma,  Italy.  —  Our  material  was 
selected  from  a  specimen  in  the  Brush  collection,  Cat.  No. 
2063,  which  had  been  presented  to  Prof.  Brush  by  Prof.  A. 
Scacchi.  The  associated  minerals  constituting  the  gangue  are 
calcite  and  biotite  (meroxene).  The  crystals  are  honey- 
yellow  in  color,  and  transparent. 

The  analyses  are  as  follows : 

Warwick,  N.  Y. 
Specific  gravity  =  3.168-3.235. 


I. 

II. 

in. 

IV. 

Average. 

Ratio. 

Si02 

33.85 

33.67 

33.82 

33.86 

33.80 

0.563 

0.563 

MgO 

55.74 

55.87 

55.78 

55.68 

55.70 

1.396  ) 

1.433 

FeO 

2.59 

2.64 

2.69 

2.64 

0.037  J 

A1203 

1.79 

1.87 

.  .  . 

.  .  . 

1.83 

.  .  . 

F 

7.32 

7.26 

7.32 

.  .  . 

7.30 

0.384  ) 

H20 

1.43 

1.48 

1.46  -f- 

9  =  0.162  J 

0.546 

102.73 

Oxygen  equivalent 

toF  = 

3.07 

99.66 


Brewster,  N.  Y. 


Specific  gravity  -  3.204-3.231. 

I.            II. 

ill. 

Average. 

Ratio. 

Si02 

33.66         33.48 

33.87 

33.67 

0.561     0.561 

MgO 

54.68         54.92 

54.78 

54.79 

L37°h452 

FeO 

5.89           5.96 

5.99 

5.94 

0.082  J 

F 

5.25           5.38 

5.31 

5.30 

0.279  ^       . 

H20 

2.60           2.44 

2.61 

2.55  -f-  9 

=  0.294  \ 

102.25 

Oxygen  equivalent  to  F  = 

2.23 

100.02 

CHONDRODITE,  HUMITE,  AND   CLINOHUMITE.       223 

Kafveltorp,  Sweden. 

Specific  gravity  =  3.252-3.265. 

I.  II.  HI.  IV.  Average.  Ratio. 

SiO2         33.36        33.28        33.18        33.52        33.33  0.556    0.556 

MgO        54.23        54.37         54.30  1.358 )      .  0 

FeO  6.66          6.58         6.62  0.092  J    ' 

F  6.74          6.58          6.63          6.43          6.60  0.347) 

H20  1.63          1.72         1.67  -f-  9  =  0.186  f 

102.52 

Oxygen  equivalent  to  F  =  2.76 

99.76 

Mte.  Somma,  Italy. 
Specific  gravity  =  3.194-3.215. 


0.564 


I.              II. 

Average. 

Ratio. 

Si02          33.96        33.78 

33.87 

0.564 

MgO         56.37        56.55 

56.46 

1.411 

FeO            3.72          3.60 

3.66 

0.050 

F                 5.09          5.21 

5.15 

0.271 

H20            2.92          2.72 

2.82  -:-  9 

=  0.313 

101.96 

Oxygen  equivalent  to  F  = 

2.16 

99.80 

In  discussing  the  above  analyses  it  has  been  assumed  that 
FeO  is  isomorphous  with  MgO  and  hydroxyl  with  fluorine. 
The  ratios  have  been  collected  together  in  the  following 
table  : 


Si02           :    (MgO  -f-  FeO)  :    (F  +  OH) 

Warwick, 

0.563      : 

1 

.433 

:      0.546  = 

1 

.96 

:  5 

:  1 

.90 

Brewster, 

0.561      : 

1 

.452 

:      0.593  = 

1 

.93 

:  5 

:  2 

.04 

Kafveltorp, 

0.556      : 

1 

.450 

:      0.533  = 

1 

.92 

:  5 

:  1 

.84 

Mte.  Somma, 

0.564      : 

1 

.461 

:      0.584  = 

1 

.93 

:  5 

:  1 

.99 

These  all  approximate  to  SiO2  :  RO  :  (F  +  OH)  =  2:5:2, 
which  would  give  for  the  formula  of  chondrodite,  Mg5[F,OH]2 
Si2O8  or  an  isomorphous  mixture  of  the  molecules  Mg3[MgF]2 
[SiO4]2  and  Mg3[MgOH]2[SiO4]2.  The  ratio  of  fluorine  to 
hydroxyl,  or  of  the  two  foregoing  molecules,  varies  consid- 


224 


ON  THE   CHEMICAL   COMPOSITION  OF 


erably.  In  the  Brewster  and  Mte.  Somma  minerals  it  is  nearly 
1  :  1,  in  Kafveltorp  2:1,  and  in  Warwick  2J  :  1.  The  specific 
gravities  are  very  close,  varying  only  between  3.165  and  3.265 
and,  as  would  be  expected,  increase  with  the  percentage  of 
iron. 

For  a  better  comparison  of  the  analyses  with  the  theory 
they  are  given  below  after  recalculating  FeO  as  MgO  and 
bringing  the  total  to  one  hundred  per  cent. 


Mte.  Somma. 


Theory  where 
F  :  OH  =  1  :  1. 


34.52 
59.56 
5.25 

2.88 

35.29 
58.82 
5.59 
2.65 

102.21 
2.21 

102.35 
2.35 

Brewster. 

Si02    .......  34.56 

MgO   .......  59.69 

F  .........     5.44 

H20     .......     2.62 

102.31 
0.  eq.  to  F  =  2.31 

Warwick. 
Si02      .......    34.91 

MgO   .......  59.23 

F  .........     7.54 

H20    .......     1.51 

103.19 
0.  eq.  to  F  =  3.19 


These  analyses  are  all  slightly  high  in  magnesia  and  corre- 
spondingly low  in  silica  and  (F  +  OH),  but  on  the  whole  they 
agree  very  well  with  the  theory. 

HUMITE  (Type  I  of  Scacchi). 

In  the  course  of  the  investigation  we  have  been  able  to 
examine  only  the  humite  from  Mte.  Somma,  of  which  two 
separate  samples  were  analyzed.  The  material  for  the  first 
of  these  was  obtained  from  a  specimen  purchased  from  Dr. 
A.  E.  Foote  of  Philadelphia.  The  humite  crystals,  which 
measure  from  2-3  mm.  in  diameter,  are  nearly  colorless  and 
transparent  and  are  associated  with  spinel  and  calcite.  Their 
habit  corresponds  in  general  to  the  figure  of  vom  Rath  copied 


Kafveltorp. 

jLiieory  wnere 
P  :  OH  =  2  :  1. 

34.42 

35.22 

59.90 

58.71 

6.81 

7.44 

1.73 

1.76 

102.86 

103.13 

2.86 

3.13 

CHONDRODITE,  HUMITE,   AND   CLINOHUM1TE.       225 

into  the  sixth  edition  of  Dana's  Mineralogy,  page  535.  The 
material  for  the  second  analysis  was  selected  from  a  specimen 
in  the  Yale  College  cabinet,  catalogue  No.  4102.  The  crys- 
tals are  associated  with  calcite  and  biotite.  They  are  chest- 
nut brown  in  color,  in  habit  like  the  ones  described  above. 

FIRST  ANALYSIS. 
Specific  gravity  =  3.194-3.201. 


I.                II.             m.             IV.          Average. 

Ratio. 

Si02 

36.59    36.63    36.63    36.68    36.63 

0.6105 

MgO 

56.34     56.43     56.59    56.45     56.45 

1.411    ) 

FeO 

2.33      2.43       2.46      2.30      2.35 

0.033    ) 

F 

3.12      3.06      2.96      .  .  .        3.08 

0.162    )  A  . 

H20 

2.42      2.48      2  45  — 

9  =  0.261    }°'423 

100.96 

Oxygen  equivalent  to  F  =         1.26 

99.70 


SECOND  ANALYSIS. 
Specific  gravity  =  3.183-3.225. 


i.              n. 

Average. 

Ratio. 

Si02         36.84        36.63 

36.74 

0.612 

MgO         56.21        56.42 
FeO            2.22          2.21 

56.31 

2.22 

1.408 
0.029 

F                3.89          4.02 

3.96 

0.208 

H20           2.18          2.08 

2.13^ 

9  =  0.236 

101.36 

Oxygen  equivalent  to  F  = 

1.66 

1.437 
444 


99.70 

These  analyses  differ  from  those  of  chondrodite  in  being 
about  3  per  cent  higher  in  silica,  and  also  the  ratios  are  differ- 
ent as  shown  by  the  following : 

Si02         :  (MgO  +  FeO)    :  (F  -f-  OH) 

1st  Analysis,  0.6105   :      1.444      :   0.423  =  2.97  :  7  :  2.05 

2d  Analysis,  0.612     :      1.437      :   0.444  =  2.99  :  7  :  2.16 

These  ratios  approximate  closely  to  3  :  7  :  2,  indicating  that 
the  formula  of  humite  is  Mg5[Mg(F,  OH)]2[SiO4]3.  The  ratio 

15 


226  ON  THE   CHEMICAL    COMPOSITION  OF 

of  F :  OH  in  the  first  analysis  is  nearly  2  :  3  and  in  the  second 
about  1  :  1.  We  give  beyond  the  theoretical  composition  for 
both  ratios,  together  with  the  analyses  in  which  the  FeO  has 
been  calculated  as  MgO  and  the  total  brought  to  100  per  cent. 

First  Theory  where  Second  Theory  where 

analysis.         P  :  OH  =  2  :  3.  analysis.  F  :  OH  =  1  :  1. 

Si02              37.15  37.53  37.24  37.50 

MgO             58.56  58.38  58.27  58.34 

F                     3.12  3.17  4.02  3.96 

H20                2.48  2.25  2.16  1.87 

101.31  101.33  101.69  101.67 

O  eq.  to  F  =  1.31  1.33  1.69  1.67 

These  analyses  show  a  very  satisfactory  agreement  with 
the  theory  and  we  may  regard  the  formula  of  humite  as  well 
established. 

CLINOHUMITE  (Humite  Type  III  of  Scacchi). 

Of  this  rare  mineral  we  have  been  able  to  examine  two 
specimens  from  Mte.  Somma.  For  the  first  analysis  the 
material  was  derived  from  a  specimen  in  the  Brush  collection, 
catalogue  No.  2064,  which  had  been  presented  by  W.  Sartorius 
von  Waltershausen.  The  crystals  are  light  wine  yellow, 
transparent  and  in  habit  like  the  simple  crystals  figured  by 
vom  Rath.  The  associated  minerals  are,  forsterite,  biotite, 
spinel,  calcite  and  a  little  vesuvianite. 

The  specific  gravity,  when  taken  with  the  heavy  solution, 
varied  between  3.184  and  3.222  and  this  being  almost  identi- 
cal with  that  of  forsterite  the  yellow  clinohumite  crystals  had 
to  be  separated  from  the  colorless  forsterite  by  hand  picking. 
The  specimen  only  afforded  0.3879  grams  of  the  mineral  and 
the  analysis  was  made  on  this  small  portion  by  fusing  the 
whole  with  dry  sodium  carbonate  in  the  Gooch  crucible  to 
obtain  the  water,  soaking  out  the  fusion  and  carrying  on  the 
analysis  in  the  usual  way.  In  the  course  of  the  analysis  an 
unusual  accident  occurred.  The  platinum  crucible  in  which 
the  fusion  was  made  broke,  and  it  was  not  discovered  till,  on 


CHONDRODITE,  HUMITE,  AND   CLINOHUMITE.       227 

soaking  out  the  fusion,  it  was  found  to  leak.  The  break  was 
of  such  a  nature  that  the  water  determination  was  not  lost 
and  the  mechanical  loss,  caused  by  the  leaking,  was  slight 
and,  in  all  probability,  evenly  distributed  on  the  remaining 
constituents.  It  is  assumed  that  the  deficiency  of  the  analysis, 
amounting  to  about  2  per  cent,  was  caused  by  this  accident, 
as  otherwise  the  analysis  was  carried  on  with  more  than  usual 
care.  The  analysis  is  given  beyond  under  a  as  it  stands  in  the 
note  book  and  under  b  after  distributing  the  deficiency  of  2.28 
per  cent  among  all  of  the  constituents  except  water. 

The  material  for  the  second  analysis  was  derived  from  a 
specimen  in  the  Yale  College  cabinet,  catalogue  No.  4143. 
The  crystals  are  chestnut  brown  in  color  and  are  associated 
with  forsterite,  biotite,  vesuvianite,  and  a  little  calcite. 

The  material  for  the  analysis  had  to  be  selected  by  hand 
picking  and,  when  introduced  into  the  heavy  solution,  showed 
a  specific  gravity  between  the  limits  3.219  and  3.258.  The 
analyses  are  as  follows: 


4.02 
205 


FIRST 

ANALYSIS. 

a. 

6. 

R 

Si02 

37.15 

38.03 

0.634 

MgO 

52.74 

54.00 

1.350] 

FeO 

4.72 

4.83 

0.067  f  1>43 

F 
H20 

2.01 
1.94 

2.06 
1.94 

°'108  I  0323 
-f-9  =  0.215  I0'323 

98.56 

100.86 

0  eq.  to  F  = 

0.84 

0.86 

97.72      100.00 

SECOND  ANALYSIS. 
2 


Ratio. 

Si0  37.78  0.629  4.03 


MgO  53.05  1-3261  OQ 

FeO  5.64  0.078  1  1>4C 

F  3.58  0.1881  „_ 

H20  1.33-^-9  =  0.148  I0'336 

101.38 

0  eq.  to  F  =  1.50 

"9^88 


228  ON   THE   CHEMICAL   COMPOSITION  OF 

In  both  of  these  analyses  the  ratios  of  SiO2 :  RO  :  (F  +  OH) 
approximate  closely  to  4  :  9  :  2,  corresponding  to  the  formula 
Mg7[Mg(F,OH)]2[SiO4]4.  In  the  first  analysis,  the  ratio  of 
F  :  OH  =  1  :  2  and  in  the  second  it  is  about  1:1.  Below 
we  have  given  the  analyses  after  calculating  FeO  as  MgO 
and  bringing  them  to  100  per  cent  and,  for  comparison,  the 
theoretical  composition  according  to  the  above  formula  with 
F  :  OH  =  1:2  and  1  :  1  respectively. 

First  Theory  where  Second  Theory  where 

analysis.  F  :  OH  —  1  :  2.  analysis.          F  :  OH  =  1  :  1. 


Si02 

38.87 

38.75 

38.81 

38.77 

MgO 
F 

57.94 
2.10 

58.12 
2.05 

57.64 
3.68 

58.16 
3.07 

H20 

1.98 

1.94 

1.37 

1.29 

100.89          100.86          101.50          101.29 
0  eq.  to  F  =       0.89  0.86  1.50  1.29 

The  agreement  of  the  above  analyses  with  the  theory  is 
very  satisfactory. 

Conclusions.  —  In  the  preceding  pages  we  have  shown  that 
the  minerals  of  the  humite  group  are  not  identical  with  each 
other  in  chemical  composition  and  that  they  can  be  expressed 
by  the  following  formula,  constructed  on  two,  three  and  four 
molecules  of  orthosilicic  acid,  in  which  two  hydrogen  atoms 
are  replaced  by  the  univalent  radical  [Mg(F,  OH)]  and  the 
remaining  ones  by  magnesium: 

Chondrodite     Mg3[Mg(F,  OH)]2[Si04]2 

Humite Mg5[Mg(F,OH)]2[Si04]3 

Clinohumite Mg7[Mg(F,  OH)]2[SiOJ4 

These  form  a  chemical  series,  varying  progressively  from 
chondrodite  to  clinohumite  by  an  increase  of  one  molecule  of 
Mg2SiO4.  This  variation  in  chemical  composition  is  intimately 
connected  with  the  crystallization.  Thus  on  page  219  it  was 
mentioned  that  the  three  minerals  form  a  crystallographic 
series  in  which  the  vertical  axes  increase  from  chondrodite  to 
clinohumite.  It  was  also  shown  that  by  dividing  the  vertical 


CHONDRODITE,   HUMITE,  AND   CLINOHUMITE.       229 

axes  by  5,  7,  and  9  respectively  the  quotients  become  practi- 
cally identical  and  it  is  a  very  interesting  and  remarkable  fact 
that  these  divisors  5  7,  and  9  correspond  to  the  number  of 
magnesium  atoms  in  the  formulae  deduced  by  us.  Groth  has 
shown  that  in  certain  organic  compounds  the  substitution  of 
one  hydrogen  atom  by  another  atom  or  radical  causes  a  change 
in  one  of  the  crystallographic  axes,  the  other  two  and  the 
symmetry  remaining  essentially  unchanged.  Such  a  crystallo- 
graphic series  he  calls  a  "  Morphotropische  Reihe."  In  the 
humite  group  we  evidently  have  a  kind  of  morphotropic 
series,  but  not  exactly  analogous  to  that  cited  by  Groth,  as 
in  the  present  case  we  have  a  change  brought  about  by  the 
addition  of  a  molecule  of  Mg2SiO4,  instead  of  the  substitution 
of  a  radical.  This  addition  of  Mg2SiO4  causes  the  vertical 
axis  to  increase  by  about  1.2575,  or  \  of  the  vertical  axis  of 
clinohumite,  while  the  other  two  axes  and  the  inclination  /3 
remain  the  same.  The  symmetry,  however,  changes  so  that 
the  first  and  last  members  of  the  series  are  monoclinic.  In 
the  whole  range  of  chemical  crystallography  there  is  no  series 
of  compounds  known  to  the  authors  that  can  be  compared 
to  the  humite  group.  It  is  reasonable  to  expect  that  other 
members  of  this  series  will  be  found.  Thus  Mg[Mg(F,  OH)]2 
SiO4  is  a  possible  and  a  most  likely  compound  to  occur. 
This  should  crystallize  either  orthorhombic  or  monoclinic 
with  /3  =  90°  and  should  have  the  axial  ratio  a  :  b  :  c  — 1.086 : 
1  :  1.887.  The  member  next  beyond  clinohumite  would  be 
Mg9[Mg(F,OH)]2[SiO4]5  but,  owing  to  its  more  complicated 
composition,  it  would  seem  less  apt  to  occur.  Chrysolite, 
Mg2SiO4,  is  closely  related  to  the  members  of  this  group,  and, 
as  shown  by  vom  Rath,*  a  few  of  its  forms  are  almost 
identical  with  those  of  humite.  Their  relation  is  shown  on 
page  219  where  the  axial  ratio  b  :  2a  :  c  of  chrysolite  is  similar 
to  a  :  b  l<?  of  clinohumite.  As  chrysolite  contains  no  fluorine 
or  hydroxyl  it  deviates  considerably  in  its  chemical  type  from 
the  members  of  the  humite  group  and  its  crystalline  habit  is 
also  different,  as  the  majority  of  its  common  forms  do  not 

*  Fogg.  Ann.,  Erganz.  Band  V,  p.  412,  1871. 


230       CHONDRODITE,  HUMITE,  AND   CLINOHUMITE. 

correspond  to  any  of  the  forms  of  humite.  Of  the  three 
species  constituting  the  humite  group  chondrodite  has  the 
simplest  composition  and  is  the  most  common,  clinohumite 
has  the  most  complicated  composition  and  is  the  rarest,  while 
humite  occupies  an  intermediate  position.  At  Mte.  Somma 
chondrodite,  which  is  the  most  basic,  occurs  usually  with 
calcite,  while  clinohumite,  which  is  the  most  acid,  is  usually 
associated  with  the  silicate  f orsterite. 

The  formulse  thus  proposed  as  the  result  of  this  investiga- 
tion are  simple  and  rational,  they  agree  in  a  very  satisfactory 
manner  with  the  results  of  our  analyses  as  well  as  with 
those  of  others,  and  they  constitute  an  extremely  interesting 
chemical  series,  which  is  related  in  a  remarkable  manner  to 
the  crystallization  of  these  minerals. 

NOTE.  —  Soon  after  the  publication  of  this  paper  Hj.  Sjogren 
(Bull.  Geolog.  Inst.  Upsala,  1894,  2,  p.  39)  published  a  series 
of  analyses  of  the  minerals  of  the  chondrodite  group  confirming 
the  results  as  set  forth  in  the  foregoing  pages.  He  also  described 
a  mineral  belonging  to  the  group  having  the  ratio  of  its  crystal- 
lographic  axes  a  :  b  :  c  =  1.0803  :  1  :  1.8862.  This  is  supposed 
to  be  the  possible  member  of  the  chondrodite  group  referred  to 
on  the  previous  page.  Although  not  found  in  sufficient  quantity 
to  admit  of  a  chemical  analysis  being  made,  the  formula  Mg 
[Mg(F,  OH)]2Si04has  been  assigned  to  it.  It  is  named  prolectite 
from  TrpoAe'yeiv,  to  foretell.  —  EDITOR. 


ON    THE    CHEMICAL    COMPOSITION    AND     RE- 
LATED PHYSICAL  PROPERTIES   OF  TOPAZ. 

BY  S.  L.  PENEIELD  AND  J.  C.  MINOR,  JR. 
(From  Amer.  Jour.  Sci.,  1894,  vol.  47,  pp.  387-396.) 

THE  chemical  composition  of  topaz  has  never  been  satisfac- 
torily settled.  The  results  of  the  analyses  thus  far  published 
show  clearly  that  silicon  and  aluminium  are  present  in  the 
proportion  of  1  :  2,  but  the  percentage  of  fluorine  as  given  in 
them  varies  from  16.12-18.83.  The  formula  that  is  usually 
accepted  is  that  of  Groth  *  [A1(O,  F2)]  AlSiO4,  corresponding 
to  an  isomorphous  mixture  of  [A1F2]  AlSiO4  with  the  andalu- 
site  molecule  [A1O]  AlSiO4  in  which  the  former  predominates 
and  in  which  fluorine  is  supposed  to  be  replaced  by  oxygen. 
Rammelsberg  f  suggests  a  mixture  of  Al2SiO5  and  Al2SiF10  in 
the  proportion  of  5  :  1.  The  ratio  of  SiO2  :  A12O3  :  F  varies 
from  1:1:  1.50  to  1  :  1  :  1.84  and  if  this  could  be  shown  to 
be  1  :  1  :  2  the  composition  could  be  expressed  by  either  of 
the  following  simple  orthosilicate  formulae: 

F-A1<°\  F 

°>Si   or   ] 


Since  it  has  been  shown  by  one  of  us  that  hydroxyl  so 
frequently  replaces  fluorine,  and  it  now  seems  very  doubtful 
if  bivalent  oxygen  ever  plays  this  r61e,  the  idea  has  suggested 
itself  that  perhaps  the  variations  in  the  percentages  of  fluorine 
and  the  failure  to  yield  a  simple  ratio  are  due  to  the  partial 

*  Tabellarische  Uebersicht  der  Mineralien,  1889,  p.  106. 
t  Mineralchemie,  1875,  p.  580. 


232         CHEMICAL   COMPOSITION  AND  RELATED 

replacement  of  fluorine  by  hydroxyl.  Accordingly  tests  were 
made  for  water  and  it  has  been  found  to  be  always  present. 
This  fact  seems  to  have  been  generally  overlooked. 

In  testing  by  the  ordinary  closed  tube  method  it  is  not 
always  evident  that  hydroxyl  is  present,  since  in  a  mineral 
like  topaz  an  acid  vapor  comes  off,  probably  hydrofluosilicic 
acid,  instead  of  water.  By  mixing  the  mineral,  however,  with 
lime  or  some  other  substance  to  hold  the  fluorine,  water  is 
evolved.  In  order  to  determine  to  what  extent  hydroxyl  is 
present  and  what  part  it  plays  in  the  chemical  composition, 
material  from  a  number  of  localities  has  been  examined,  and 
it  will  be  shown  in  the  course  of  this  article  that  the  varia- 
tions which  topaz  shows  both  in  chemical  composition  and 
physical  properties  result  from  an  isomorphous  replacement 
of  fluorine  by  hydroxyl,  while  a  simple  composition  has 
been  established  which  can  be  expressed  by  the  formula 
[A1(F,  OH)]2SiO4. 

Method  of  analysis.  —  The  important  features  of  the  analy- 
sis were  of  course  the  accurate  determination  of  fluorine  and 
water.  For  fluorine  the  method  of  Berzelius  was  adopted. 
The  mineral  mixed  with  half  its  weight  of  quartz,  was  fused 
with  five  times  the  total  weight  of  mixed  sodium  and  potas- 
sium carbonates.  The  fusion  was  soaked  out,  filtered  and 
washed  with  hot  water.  To  the  hot  filtrate  five  to  ten  grams 
of  ammonium  carbonate  were  added  and  after  cooling,  still 
another  addition  of  the  same  reagent.  After  standing  in  the 
cold  for  twelve  hours  the  precipitate  was  filtered  off,  the 
excess  of  ammonium  carbonate  expelled  from  the  filtrate  by 
heating  in  a  platinum  dish  on  the  water  bath,  and  an  ammo- 
niacal  solution  of  zinc  oxide  added.  After  evaporating  until 
the  odor  of  ammonia  had  disappeared  the  zinc  oxide  precipitate 
was  removed  by  filtration,  the  filtrate  heated  and  dilute  nitric 
acid  added  until  the  excess  of  alkali  carbonate  was  nearly 
decomposed.  To  the  slightly  alkaline  boiling  solution  an 
excess  of  calcium  chloride  was  added  and  from  this  point  the 
precipitate  was  treated  as  previously  described  by  one  of  us.* 

*  Amer.  Jour.  Sci.,  1894,  vol.  47,  p.  190. 


PHYSICAL  PROPERTIES  OF  TOPAZ.  233 

That  determinations  made  by  this  method  are  satisfactory 
was  proved  by  the  following:  In  an  experiment  with  topaz 
the  residue  resulting  from  soaking  out  the  alkali  carbonate 
fusion,  and  the  precipitates  formed  by  the  ammonium  car- 
bonate and  zinc  oxide  were  united,  mixed  with  a  fresh  portion 
of  alkali  carbonates,  fused  and  treated  as  before.  The 
amount  of  fluorine  that  was  obtained  by  this  second  treatment 
was  only  0.07  per  cent,  showing  that  practically  all  may  be 
extracted  by  one  fusion.  Moreover,  fluorine  determinations 
were  made  by  the  above  method  in  an  artificial  mixture  of 
cryolite,  cyanite,  and  quartz,  taken  in  proportions  to  cor- 
respond with  the  composition  of  topaz  with  the  following 
results  : 

Cryolite  taken.  •  Fluorine  calculated.  Fluorine  found.  Loss. 

0.3325  0.1805  0.1788  0.0017 

This  result  indicates  only  a  slight  deficiency,  and  it  is  probable 
that  the  determinations  in  the  regular  topaz  analyses  are  not 
over  0.20  per  cent  low,  as  usually  a  gram  and  sometimes  a 
gram  and  a  half  of  the  mineral  were  taken  for  a  determination. 
In  the  above  no  allowance  has  been  made  for  what  might  be 
recovered  by  a  second  fusion  of  the  residues,  and  probably 
some  of  the  loss  is  occasioned  by  volatilization  during  the  alkali 
carbonate  fusion,  but  since  the  crucible  was  kept  covered  this 
must  have  been  very  slight.  Since  water  is  present,  it  is 
evident  that  attempts  that  have  been  made  to  determine 
fluorine  by  loss  on  ignition,  assuming  that  silicon  fluoride  is 
given  off,  cannot  have  given  reliable  results.  For  the  deter- 
mination of  water,  the  mineral  has  been  fused  with  dry  sodium 
carbonate  and  the  water  absorbed  in  a  weighed  sulphuric  acid 
tube.  The  method,  which  has  been  carefully  tested,  gives 
accurate  results.  The  mineral  is  completely  decomposed  and 
it  is  impossible  for  acid  vapors  to  pass  off  with  the  water. 
There  can  be  no  doubt  about  the  water  having  come  from 
hydroxyl,  since  it  is  not  driven  off  except  at  an  intense  heat. 
In  an  experiment  on  topaz  from  Stoneham,  Me.,  where  the 


234         CHEMICAL   COMPOSITION  AND  RELATED 

water  was  found  to  be  0.98  per  cent,  the  powder  suffered  a 
loss  of  only  0.12  per  cent  by  heating  for  a  long  time  in  a 
platinum  crucible  at  the  highest  heat  of  a  ring  burner. 

The  remainder  of  the  analysis  was  conducted  in  the  ordinary 
manner. 

Material  for  analysis.  —  The  specimens  which  we  have 
examined  are.  from  the  following  localities : 

Stoneham,  Maine. — The  material  was  colorless  and  trans- 
parent and  was  taken  from  the  center  of  a  large  crystal  in  the 
Brush  collection,  catalogue  number  185.  Analyses  have  also 
been  made  by  Genth*  and  Whitneld.f  The  former  found 
18.83  and  the  latter  17.10  per  cent  of  fluorine,  also  Na2O  1.25, 
K2O  0.14  and  H20  0.20  per  cent.  A  careful  test  that  we  have 
made  for  alkalies  has  shown  that  they  are  absent. 

Pike's  Peak,  Colorado.  —  A  perfectly  colorless  and  trans- 
parent cleavage  piece  from  a  large  crystal. 

Nathrop,  Colorado.  --  Wine  yellow  crystals  in  rhyolite, 
described  by  Cross,  t  The  habit  is  similar  to  figure  4,  page 
493  of  the  sixth  edition  of  Dana's  Mineralogy,  or  figure  54, 
page  123  of  Hintze's  Mineralogy. 

Utah.  —  Perfectly  colorless  transparent  crystals  from  the 
rhyolite  of  the  Thomas  Range,  forty  miles  north  of  Sevier 
Lake.  The  crystals  were  selected  from  a  suite  of  speci- 
mens in  the  Brush  collection,  and  have  been  described  by 
A.  N.  Alling.§ 

San  Luis  Potosi,  Mexico.  —  Colorless,  transparent  crystals 
like  those  described  by  Bucking  ||  and  similar  to  the  ones 
from  Nathrop. 

Zacatecas,  Mexico.  —  Colorless  crystals  similar  to  the  pre- 
ceding. The  material  was  generously  supplied  to  us  by  Prof. 
A.  J.  Moses,  from  the  mineralogical  collection  of  the  Columbia 
School  of  Mines,  New  York. 


*  Trans.  Am.  Phil.  Soc.  Oct.,  1885,  p.  43. 

t  Amer.  Jour.  Sci.,  1885,  vol.  29,  p.  378. 

|  Ibid.,  1886,  vol.  31,  p.  443. 

§  Ibid.,  1887,  vol.  33,  p.  146. 

||  Zeitschr.  Kryst.,  xii,  p.  424,  1886. 


PHYSICAL  PROPERTIES   OF  TOPAZ. 


235 


Schneckemtein,  Saxony. — Wine  yellow  crystals,  selected 
from  a  suite  of  specimens  in  the  Brush  collection. 

Adun-Chalon,  Siberia.  —  The  specimen  corresponded  to 
the  description  given  by  Kokscharow.*  A  colorless  and 
transparent  crystal  in  the  Brush  collection  was  used  for  the 
analysis. 

Tenagari,  Mino,  Japan.  —  The  material  was  taken  from  a 
colorless,  transparent  crystal,  in  habit  like  those  from  Adun- 
Chalon. 

Minas  Greraes,  Brazil.  —  Transparent,  yellow  crystals  se- 
lected from  a  suite  of  specimens  in  the  Brush  collection. 

We  take  pleasure  in  expressing  to  Mr.  Geo.  L.  English  of 
New  York  our  thanks  for  generously  supplying  us  with  the 
specimens  from  Nathrop,  San  Luis  Potosi  and  Japan. 

The  following  complete  analyses  have  been  made : 


Si02 

A1A 

F 

H20 


31.93 

56.26 

20.33 

0.19 


20.41 


Utah. 


II.          Average. 


Ratio. 


0  equivalent  to  F. 


31.93 
56.26 

20.37  1.072 

0.19  -=-  9  =  0.021 


0.532 
0.551 


0.98 
1.015 


1.093    2.02 


108.75 

8.58 

100.17 


Theory  for 
[AlF]2Si04. 

32.61 
55.44 
20.65 

108.70 

8.70 

100.00 


Si02 
A1208 
F 
H20 

0  equivalent  to  F. 


Nathrop,  Colorado. 

32.23 
56.01 

20.42  1.075 

0.29  -T-  9  =  0.032 


Ratio. 

0.537        0.99 
0.550        1.01 

1.107        2.03 


108.95 

8.60 

100.35 


*  Materialien  zur  Min.  Russlands,  II,  p.  232. 


236 


CHEMICAL   COMPOSITION  AND  RELATED 


Si02 
A1A 
F 
H20 


i. 

32.28 

56.61 

19.41 

0.57 


IT, 


19.60 


O  equivalent  to  F. 


Japan. 

Average. 

32.28 
56.61 
19.50 


Ratio. 


1.027  ) 


0.57  -f-  9  =  0.063  f 


0.538 
0.555 

1.090 


0.98 
1.02 

2.00 


108.96 
8.21 

100.75 


Si02 
A120£ 
F 
H20 


Schneckenstein,  Saxony. 

Ratio. 

32.82  0.547  1.00 

55.41  0.543  1.00 

18.50  0.974 

0.93  +  9  =  0.103 


107.66 


O  equivalent  to  F.       7.80 
99.86 


1.97 


n. 


Stoneham,  Maine. 

Average. 


Ratio. 


Theory  for 


Si02 
A1203 

32.28    32.40 
56.33    56.33 

32.34                         0.539    0 
56.33                         0.552    1 

.99      32.68 
.01      55.56 

F 

18.56     18.30 

18.43             0.970  )  .  AOA 

18.63 

H20 

1.04      0.93 

0.98  H-  9  =  0.110  I1'080    * 

•98        0.98 

108.08 

0  equivalent  to  F.  7.76 

100.32 


107.85 

7.85 

100.00 


Si02 
A120; 
F 
H20 


O  eq.  to  F. 


32.53 
55.67 
15.48 


0.815 


2.45  -^  9  =  0.272  j 


106.13 
6.52 


Ratio. 

Theory  where 
F  :  OH  =  3  :  1. 

0.542 

1.00 

32.79 

0.546 

1.00 

55.74 

1.087 

2.01 

15.57 
2.45 

106.55 

6.55 

100.00 

PHYSICAL  PROPERTIES   OF   TOPAZ.  237 

From  the  results  of  these  analyses  it  is  evident  that  fluor- 
ine has  been  replaced  by  hydroxyl,  and  the  ratios  indicate 
very  clearly  that  SiO2  :  A12O3  :  F+OH  =  1  :  1 :  2  as  re- 
quired by  either  of  the  following  formulae  [Al(F,OH)]2SiO4  or 
[Al(F,OH)2]AlSiO4.  The  first  two  analyses  show  very  little 
hydroxyl,  so  that  the  material  may  be  regarded  as  practically 
the  pure  fluorine  compound,  [AlF]2SiO4.  In  addition  to  the 
complete  analyses,  isolated  determinations  have  been  made  on 
material  from  the  other  localities  mentioned  on  pages  234  and 
235,  and  these  results  will  be  given  beyond  in  tabular  form. 

Physical  properties  and  their  relations  to  the  chemical  com- 
position. —  The  specific  gravities  were  very  carefully  deter- 
mined on  a  chemical  balance,  pains  being  taken  to  boil  the 
crystals  for  some  time  in  water  to  expel  any  air  bubbles.  The 
results  vary  within  the  limits  3.574  and  3.533,  a  difference  of 
only  0.041,  and  as  a  rule  they  decrease  as  the  molecularly 
lighter  hydroxyl  replaces  fluorine. 

Also  basal  plates  were  prepared  and  the  divergence  of  the 
optical  axes  2E  measured  on  a  large  axial  angle  apparatus. 
The  values  for  2E  have  been  found  to  vary  in  topaz  from  dif- 
ferent localities  and  according  to  the  observations  of  Des 
Cloizeaux  they  extend  from  129°  30'  on  crystals  from  Du- 
rango,  Mexico*  to  71°  32'  on  those  from  Mugla,  in  Natolien, 
Asia  Minor,!  both  measurements  being  for  red.  These  varia- 
tions have  generally  been  supposed  to  be  connected  with  some 
change  in  chemical  composition,  but  a  satisfactory  explanation 
has  never  been  given.  In  the  following  table  the  measure- 
ments that  we  have  made  are  arranged  according  to  decreasing 
values  of  2E  for  yellow,  and  with  these  the  determinations  of 
the  specific  gravity,  fluorine  and  water  are  given : 

2E  yellow.  ^cific  Fiuorine.  Water. 

Zacatecas,  Mexico,  126°  28'  3.574  ...  0.18 

Thomas  Kange,  Utah,  125°  53'  3.565  20.37  0.19 

Nathrop,  Colorado,  125°  51'  3.567  20.42  0.29 

Pike's  Peak,  Colorado,  122°  42'  3.567  .  .  .  0.48 

*  Bull.  Soc.  Min.  de  France,  ix,  p.  135,  1880. 
t  Nouv.  rech.,  Inst.  France,  xviii,  p.  612. 


238 


CHEMICAL   COMPOSITION  AND  RELATED 


Tenagari,  Japan, 
Adun-Chalon,  Siberia, 
San  Luis,  Mexico, 
Schneckenstein,  Saxony,  114 
Stoneham,  Maine, 
Minas  Geraes,  Brazil, 


2B  yellow. 

Specific 
gravity. 

Fluorine. 

Water. 

120°  59' 

3.565 

19.50 

0.57 

118°  46' 

3.562 

19.24 

0.58 

118°  17' 

3.575 

19.53 

0.80 

114°  28' 

3.555 

18.50 

0.93 

113°  50' 

3.560 

18.56 

0.98 

84°  28' 

3.532 

15.48 

2.45 

. 

3.523 

2.50 

On  the  last  mentioned  crystal  the  value  of  2E  was  not 
measured  owing  to  the  strong  optical  anomalies  which  the  sec- 
tion presented ;  it  was  observed,  however,  that  the  angle  was 
small.  It  is  evident  from  the  results  given  in  the  table  that 
the  value  of  2E  decreases  as  the  percentage  of  water  increases 
or  as  fluorine  is  replaced  by  hydroxyl,  and  this  relation  is  so 
constant  that  the  percentage  of  water  can  be  told  from  the 
value  of  2E.  It  is  evident,  therefore,  that  the  topaz  from  Du- 
rango,  mentioned  by  DesCloizeaux  as  giving  the  largest  value 
of  2E  (129°  30')  must  be  the  nearest  approach  to  the  fluorine 
compound,  while  that  from  Asia  Minor,  also  cited  by  him  as 
giving  the  smallest  value  of  2E  (71°  32')  must  be  the  richest 
in  water  or  hydroxyl  and  poorest  in  fluorine  of  any  topaz  that 
has  thus  far  been  examined. 

The  indices  of  refraction  also  show  a  progressive  change 
along  with  the  variations  of  2E  as  may  be  seen  by  the  follow- 
ing determinations,  given  for  yellow  light  by  different  in- 
vestigators. 


Thomas  Range,  Utah,* 
Nerchinsk,  Adun-Chalon  Mts.,t 
Colorless  Crystal,  Brazil, f 
Schneckenstein,  Saxony,t 
"       § 
Minas  Geraes,  Brazil,! 


2E. 

2V. 

a. 

£• 

y- 

126°  24' 

67°  18' 

1.6072 

1.6104 

1.6176 

121°  55' 

65°  30£' 

1.61327 

1.61597 

1.62252 

120°  40' 

65°  14' 

1.6120 

1.6150 

1.6224 

114°  17' 

62°  33' 

1.61549 

1.61809 

1.62500 

110°  127 

60°  55' 

1.6156 

1.6180 

1.6250 

86°  21' 

49°  37' 

1.62936 

1.63077 

1.63747 

*  Ailing.    Amer.  Jour.  Sci.,  1887,  vol.  33,  p.  146. 

t  Miilheims.    Zeitschr.  Kryst.,  xiv,  p.  226,  1888. 

J  Des  Cloizeaux.    Manuel  de  Mineralogie,  p.  475,  1862. 

§  Zimanyi.    Zeitschr.  Kryst.,  xxii,  p.  339,  1893. 


PHYSICAL  PROPERTIES  OF  TOPAZ.  239 

As  hydroxyl  replaces  fluorine,  therefore,  the  indices  of  refrac- 
tion increase  and  the  strength  of  the  double  refraction  de- 
creases, as  shown  by  the  values  7  —  a  in  the  extremes : 

Thomas 'Range,  Utah  y  —  a  =  0.0104 
Minas  Geraes,  Brazil  y  -  a  =  0.00811 

The  crystallographic  axes  are  also  affected  by  the  isomorph- 
ous  replacement  of  fluorine  by  hydroxyl.  The  variation 
however  is  not  very  great  and  only  exact  determinations  can 
be  used  for  showing  it.  Mr.  C.  A.  Ingersoll  has  kindly  made 
for  us  some  careful  measurements  on  a  crystal  from  the 
Thomas  Range,  Utah,  which,  next  to  the  topaz  from  Zacate- 
cas,  contains  the  least  water  of  any  examined  by  us,  and  upon 
which  the  forms  o  (221)  and/,  (021)  were  well  developed  and 
gave  beautiful  reflections.  Also  on  one  from  Brazil  upon 
which  very  exact  measurements  could  be  obtained  from  the 
/  (021)  faces  only,  the  other  forms,  the  striated  prism  and 
the  pyramid  u,  (HI)  not  being  suitable  for  measurement. 

Utah. 

Measured.  Measured.  Calculated. 

/A/,  021  A  021  =  87°  19'        o  A  o,  221  A  221  =  105°  10'        105°  10' 
o  A  o,  221  A  221  -  49°  86'        o  A  o,  221  A  221  =  127°  47'        127°  5V 

Brazil. 

Measured. 

/A/,  021  A  021  =  86°  55|' 

The  axial  ratios  are  given  in  the  following  table  and  with 
them  a  number  of  others  given  by  investigators  who  regard 
them  as  very  exact. 

a  :  b  :  c 

Utah,  Ingersoll 0.528110  :  1  :  0.477115 

Urals,  Koksharov* 0.528542  :  1  :  0.476976 

Schneckenstein,  Laspeyres  f  .  0.531548  :  1  :  0.475973 
Brazil,  Ingersoll :  1  :  0.473862 

Optical  anomalies.  —  Of  the  crystals  examined  by  us  the 
only  ones  that  showed  optical  anomalies  were  those  from 

*  Materialien  zur  Min.  Russ.,  ii,  p.  198,  1854. 
t  Zeitschr.  Kryst.,  i,  p.  351, 1877. 


240         CHEMICAL   COMPOSITION  AND  RELATED 

Brazil.  A  basal  section  of  the  crystal  that  was  used  for  the 
complete  analysis  showed  an  interior  rhomb,  having  the  out- 
line of  the  unit  prism,  surrounded  by  four  symmetrical  trape- 
ziums, and  two  opposite  V-shaped  segments,  with  their  angles 
turned  toward  and  touching  the  acute  angles  of  the  inner 
rhomb.  The  disposition  of  the  parts  was  practically  like  that 
described  by  Mallard  *  and  Mack.f  The  extinction  directions 
of  the  outer  segments  corresponded  almost  exactly  to  that  of 
the  inner  rhomb.  On  another  crystal  from  Brazil,  for  which 
only  the  specific  gravity  and  water  determinations  are  given, 
the  optical  anomalies  were  much  more  marked,  and  the  ex- 
tinction in  the  different  segments  undulatory,  so  that  the 
divergence  of  the  optical  axes  2E  could  not  be  measured. 
When  the  sections  were  examined  by  transmitted  light  it  was 
evident  that  they  were  not  homogeneous,  since  the  well  de- 
fined outlines  between  the  inner  rhomb  and  outer  segments 
indicated  a  variation  in  the  refractive  indices.  The  structure 
indicates  very  clearly  the  existence  of  an  inner  core  or  older 
crystal,  surrounded  by  a  later  growth  of  topaz  of  different 
composition.  This  idea  agrees  with  the  observations  of  Des 
Cloizeaux,  who  found  that  the  central  and  outer  segments  of 
a  zonal  crystal  gave  different  values  for  2E.  Since  it  has 
been  shown  that  the  physical  properties  vary  with  the  com- 
position all  the  changes  to  which  such  a  compound  crystal 
is  subjected  must  give  rise  to  mechanical  strains  and  cause 
the  disturbance  in  the  optical  orientation  of  the  different 
zones. 

Comparison  between  topaz  and  herderite.  —  The  changes 
that  have  been  brought  about  by  the  partial  substitution  of 
fluorine  by  hydroxyl  have  previously  been  studied  by  one  of 
us,J  and  it  will  be  interesting  in  closing  to  make  a  compari- 
son of  the  results  that  have  been  obtained.  In  herderite 
we  know  the  pure  hydroxyl  compound,  hydro-herderite, 
Ca[BeOH]PO4,  and  the  hydrofluor-herderite,  Ca[Be(OH,F)] 
PO4,  with  OH  :  F  =  3  :  2.  With  topaz  the  nearly  pure 

*  Ann.  Mines,  x,  p.  155,  1876.  t  Wied.  Ann.,  xxviii,  p.  153,  1886. 

t  Amer.  Jour.  Sci.,  1894,  vol.  47,  p.  329. 


PHYSICAL  PROPERTIES  OF  TOPAZ.  241 

fluorine  extreme  is  known,   [AlF]2SiO4,  and  the  hydrofluor- 
topaz  from  Brazil,  [Al(F,OH)]2SiO4,  with  F  :  OH  =  3  :  1. 

In  both  herderite  and  topaz  an  increase  in  hydroxyl  is 
accompanied  by  a  decrease  in  specific  gravity  and  an  increase 
in  the  indices  of  refraction.  In  monoclinic  herderite  the  axes 
of  greatest  and  least  elasticities  correspond  nearly  to  the  crys- 
tallographic  axes,  and  overlooking  this  slight  deviation  the 
optical  orientation  in  both  minerals  is  the  same,  a  =  a,  fc  =  b 
and  c  =  c.  Since  topaz  is  positive  and  herderite  negative  the 
acute  bisectrices  are  c  and  a  respectively,  but  the  angle  of  the 
optical  axes  measured  in  each  mineral  over  the  axis  of  least 
elasticity  (that  is  in  herderite  over  the  obtuse  bisectrix)  is 
smaller  for  the  hydroxyl  than  for  the  fluorine  compound.  In 
both  minerals  the  substitution  of  hydroxyl  for  fluorine  causes 
a  change  in  the  lengths  of  the  crystallographic  axes  but  the 
changes  are  not  of  the  same  character,  since  in  herderite  the 
a  and  c  axes  both  increase  while  with  topaz  a  increases  and  c 
decreases. 


16 


ON  CANFIELDITE,  A  NEW  SULPHOSTANNATE  OF 
SILVER,   FROM  BOLIVIA. 

BY  S.  L.  PENFIELD. 
(From  Amer.  Jour.  Sci.,  1894,  vol.  47,  pp.  451-454.) 

IN  the  August  number  of  the  American  Journal  of  Science, 
1893,  page  107  (page  198  of  this  volume)  the  author  de- 
scribed as  a  new  species  a  germanium  mineral  from  Bolivia, 
to  which  the  name  canfieldite  was  given.  It  was  shown  that 
the  mineral  was  identical  with  argyrodite  in  chemical  compo- 
sition, but  differed  apparently  in  crystallization,  canfieldite 
being  isometric  while  argyrodite  was  monoclinic,  according 
to  the  description  of  Weisbach.*  The  discovery  of  the  iso- 
metric mineral  was  communicated  by  letter  to  Professor 
Weisbach,  and  soon  after  the  publication  of  the  author's  arti- 
cle a  reply  was  received  from  him,  in  which  it  was  stated  that 
better  crystals  of  the  Freiberg  argyrodite  than  those  originally 
described  had  been  examined,  and  the  results  had,  shown  that 
they  were  isometric  and  tetrahedral.  These  conclusions  have 
since  been  published,  f  The  forms  m  and  o  of  Weisbach  J  are 
regarded  as  the  dodecahedron  (11 0),/  and  k  as  the  tetrahedron 
(111),  and  v  as  the  negative  pyramidal-tetrahedron  (311). 
Argyrodite  being  isometric  it  is  evident  that  the  Bolivian 
mineral  is  not  a  new  species  and  the  name  canfieldite  is 
therefore  withdrawn.  For  the  sake  of  simplicity  it  is  a  satis- 
faction to  have  the  Bolivian  mineral  identical  with  that  from 
Freiberg,  and  it  is  regretted  that  the  isometric  character  of 
argyrodite  was  not  made  known  before  the  publication  of  the 
original  canfieldite  paper. 

*  Jahrb.  f.  Min.,  1886,  ii,  p.  67.  t  Jahrb.  f.  Min.  1894,  i,  p.  98. 

J  Compare  figure  in  Dana's  Mineralogy,  sixth  edition,  p.  150. 


ON  CANFIELDITE.  243 

There  has  also  recently  come  into  the  author's  possession, 
through  the  kindness  of  Mr.  Wm.  E.  Hidden  of  New  York,  a 
specimen  from  La  Paz,  Bolivia,  which  was  supposed  to  be 
argyrodite.  Its  total  weight  was  a  little  over  seven  grams  and 
it  consisted  of  a  few  attached  octahedrons,  modified  by  dodeca- 
hedron planes,  the  largest  crystal  measuring  13  mm.  in  axial 
diameter.  The  only  visible  impurity  was  a  very  little  metallic 
silver  in  wire  form,  deposited  in  a  few  places  on  the  outside  of 
the  crystals.  The  mineral  is  almost  identical  with  argyrodite 
in  all  of  its  physical  properties.  The  luster  is  brilliant  metal- 
lic. Color  black  with  the  same  bluish  to  purplish  tone 
observed  on  argyrodite.  The  fracture  is  irregular  to  small 
conchoidal.  Very  brittle.  Hardness  2J— 3,  specific  gravity 
6.276,  that  of  argyrodite  from  Bolivia  being  6.266.  Heated  be- 
fore the  blowpipe  on  charcoal  at  the  tip  of  the  blue  cone  the 
mineral  fuses  at  about  2  and  yields  a  coating  of  the  mixed 
oxides  of  tin  and  germanium.  This  is  white  to  grayish  near 
the  assay,  tinged  on  the  outer  edges  with  yellow.  By  con- 
tinued heating  a  globule  of  silver  results,  but  this  is  covered  by 
a  scale  or  coating  of  tin  oxide.  If  the  coating  on  the  charcoal 
is  scraped  together  and  fused  in  the  reducing  flame  with 
sodium  carbonate,  globules  of  tin  are  formed.  In  the  closed 
tube  sulphur  is  given  off  and  at  a  high  temperature  a  slight 
deposit  of  germanium  sulphide,  which  fuses  to  globules,  is 
formed  near  the  assay.  In  the  open  tube  sulphur  dioxide  is 
given  off  but  no  sublimate  is  deposited. 

The  following  method  was  adopted  for  the  analysis.  The 
mineral  was  oxidized  by  concentrated  nitric  acid  and  the  ex- 
cess of  the  latter  removed  by  evaporation.  The  residue  after 
moistening  with  nitric  acid  was  digested  with  boiling  water  for 
some  tune  and  the  insoluble  metastannic  acid  filtered  off. 
This  was  transferred  while  still  moist  to  a  beaker  and  treated 
with  strong  ammonia  into  which  hydrogen  sulphide  was  con- 
ducted until  the  metastannic  acid  had  gone  into  solution.  A 
slight  insoluble  residue  was  filtered  off  at  this  point  which 
contained  about  0.10  per  cent  of  tin  and  0.40  per  cent  of  silver. 
From  the  ammonium  sulphide  solution  the  tin  was  precipi- 


244  OZV   CANFIELDITE, 

tated  by  addition  of  a  little  sulphuric  acid  and  weighed  as 
oxide.  The  nitrate  from  the  stannic  sulphide  was  evaporated 
and  yielded  a  little  germanium  which  had  not  been  separated 
from  the  tin  by  the  nitric  acid  treatment.  In  the  original  ni- 
trate from  the  metastannic  acid,  silver  was  precipitated  by 
means  of  hydrochloric  acid  and  weighed  as  chloride.  The 
sulphur  was  next  precipitated  by  barium  nitrate,  and  after 
purifying  by  fusion  with  sodium  carbonate  weighed  as  barium 
sulphate.  Before  evaporating  the  filtrates  hydrochloric  acid 
and  barium  were  removed  by  precipitation  with  silver  nitrate 
and  sulphuric  acid.  The  excess  of  silver  was  finally  removed 
by  ammonium  thiocyanate  and  the  germanium  obtained  from 
the  filtrate  as  described  in  a  previous  communication.*  The 
results  of  the  analysis  are  as  follows  : 


S     .....  16.22  0.507  5.92            16.56 

S*   .....  6.94  0.0589  1  7.18 

Ge  .....  1.82  0.0253  }°  1.83 

Ag  .....  74.10  0.686  8.00            74.43 

Zn  and  Fe  0.21           ...  ...  ... 

99.29  100.00 

In  this  compound  tin  is  undoubtedly  isomorphous  with  ger- 
manium, and  the  two  are  present  in  about  the  proportion  12  :  5. 
The  ratio  of  S  :  Sn+Ge  :  Ag  in  the  analysis  is  very  close  to 
6:1:8,  indicating  that  the  formula  is  Ag8(Sn,Ge)S6  or 
4Ag2S  .  (Sn,Ge)S0.  The  agreement  between  the  theory  and 
the  analysis  is  satisfactory. 

The  only  sulphostannates  thus  far  known  to  occur  in  nature 
are  the  rare  species  stannite,  Cu2S  .  FeS  .  SnS2,  franckeite, 
5PbS  .  Sb2S3  .  2SnS2,  Cylindrite  (Kylindrit),  6PbS  .  Sb2S3  . 
6SnS2,  recently  described  by  Frenzel,f  and  plumbostannite,  a 
mineral  of  doubtful  composition  containing  Pb,  Fe,  Sb,  and 
S,  described  by  Raimondi.J  Franckeite  has  recently  been  de- 
scribed by  Stelzner,  §  and  in  it  Winkler  was  able  to  identify 

*  Page  202.  t  Jahrb.  Min.,  1893,  IT,  p.  125. 

t  Zeitschr.  Kryst.,  vi,  p.  632,  1882.    §  Jahrb.  Min.,  1893,  II,  p.  114. 


A   NEW  SULPHOSTANNATE   OF  SILVER.  245 

a  small  amount  of  germanium,  probably  about  0.10  per  cent. 
These  authors  call  attention  to  the  fact  that  since  tin  and 
germanium  belong  to  the  same  chemical  group  they  are 
isomorphous  with  one  another  and  suggest  the  probability 
of  finding  in  Bolivia  a  sulphostannate  of  silver  isomorphous 
with  argyrodite.  The  new  mineral  described  in  this  article 
corresponds  precisely  to  this  idea.  As  the  Freiberg  argyrodite 
has  been  shown  to  be  isometric,  and  the  name  canfieldite  can- 
not therefore  be  applied  to  the  germanium  compound,  it  is 
proposed  now  to  transfer  the  name  to  the  new  isomorphous 
tin  compound.  It  is  not  probable  that  this  will  cause  con- 
fusion as  the  name  as  at  first  applied  was  not  long  in  use  and 
has  never  been  introduced  into  any  of  the  text-books  or  sys- 
tems of  mineralogy,  and  especially  as  it  is  now  transferred  to 
a  species  which  is  very  closely  related,  and  should  come  next 
to  argyrodite  in  a  natural  system  of  classification.  It  is  prob- 
able that  various  mixtures  of  argyrodite  Ag8GeS6  and  the 
molecule  Ag8SnS6  will  be  found  and  it  would  seem  best  to 
consider  this  latter  as  the  canfieldite  molecule,  while  the  inter- 
mediate isomorphous  mixtures  would  be  called  argyrodite  or 
canfieldite,  according  as  the  germanium  or  the  tin  molecule 
predominated. 

Regarding  the  crystallization  of  the  argyrodite  and  can- 
fieldite from  Bolivia  the  specimens  examined  by  the  author 
are  apparently  holohedral.  The  octahedron  faces  are  equally 
developed  and  have  the  same  luster.  There  is,  however,  on 
each  of  the  dodecahedral  faces  of  the  canfieldite  specimen  a 
distinct  furrow  or  slight  depression  running  in  the  direction  of 
the  longest  diagonal.  This  may  indicate  a  twinning  which  has 
given  rise  to  the  apparently  holohedral  form,  or  the  latter  may 
of  course  have  resulted  from  an  equal  development  of  positive 
and  negative  tetrahedrons. 


ON  THE   OCCURRENCE   OF   THAUMASITE  AT 
WEST  PATERSON,   NEW   JERSEY. 

BY  S.  L.   PENFIELD  AND  J.   H.   PRATT. 
(From  Amer.  Jour.  Sci.,  1896,  vol.  i,  pp.  229-233.) 

IN  1878  Baron  von  Nordenskiold*  described  a  mineral  from 
the  copper  mines  of  Areskuta,  Jemtland,  Sweden,  which, 
according  to  the  analyses  of  Lindstrom,f  had  the  composition 
CaSiO3 .  CaCO3 .  CaSO4 . 14H2O  and  to  which  the  name  thau- 
masite  was  given,  from  Oav^d^eiv^  to  le  surprised.  The  min- 
eral was  not  found  in  distinct  crystals  but  was  crystalline,  and 
on  a  fracture  showed  a  fine  fibrous  structure.  Its  homogenous 
character  and  its  right  to  be  considered  a  distinct  mineral 
species  rested  upon  the  following :  The  material  seemed  to  be 
homogeneous  when  examined  with  the  microscope,  and  the 
three  analyses  of  Lindstrb'm,  made  upon  material  collected  in 
the  early  part  of  this  century  by  Polheimer,  in  1859  by  Nor- 
denskiold, and  in  1878  by  Engberg,  agreed  not  only  very 
closely  with  one  another  but  also  with  the  theory  demanded 
by  the  formula. 

That  a  mineral  with  such  a  remarkable  composition  was 
capable  of  existence  was  not  accepted  by  all  mineralogists,  and 
Bertrand,f  on  examining  thin  sections  of  it  with  the  microscope, 
was  led  to  believe  that  it  was  a  mixture,  composed  of  a  uniaxal 
mineral  with  negative  double  refraction  supposed  to  be  calcite, 
of  a  biaxial  mineral  gypsum,  and  of  a  third  mineral,  the  optical 
properties  of  which'  could  not  be  made  out,  probably  calcium 
silicate  or  wollastonite. 

The  idea  of  Bertrand's  that  thaumasite  was  a  mixture  was 
not  accepted  by  Nordenskiold,  and  the  latter  to  sustain  his 

*  Comptes  rendus,  vol.  Ixxxvii,  p.  313,  1878. 

t  Ofv.  Ak.  Stockholm,  vol.  xxxv,  No.  9,  p.  43,  1878. 

\  Bull.  Soc.  Min.  de  France,  vol.  iii,  p.  159,  1880,  and  vol.  iv,  p.  8,  1881. 


THAUMASITE  FROM   WEST  PATERSON,   N.  J.       247 

position  presented  the  following  arguments,*  which  were  very 
convincing:  First,  if  it  were  possibly  a  mixture  it  certainly 
would  be  very  remarkable  that  three  independent  samples, 
collected  at  such  widely  separated  periods,  should  agree  so 
closely  in  percentage  composition.  Second,  there  is  no  known 
hydrated  calcium  silicate  which,  when  mixed  with  calcite  and 
gypsum,  could  yield  a  product  containing  over  42  per  cent  of 
water.  Third,  it  would  not  be  possible  for  a  mixture  of  cal- 
cite, gypsum  and  wollastonite,  with  specific  gravities  of  2.72, 
2.31,  and  2.90  respectively,  to  yield  a  product  with  such  a  low 
specific  gravity  as  thaumasite,  1.877. 

Specimens  were  moreover  sent  to  Lacroix  for  renewed 
optical  examination,  and  in  a  letter  to  Nordenskiold  he  states  f 
that  the  material  was  found  to  be  practically  homogeneous, 
unaxial  and  with  negative  double  refraction,  but  whether 
hexagonal  or  tetragonal  could  not  be  determined.  The  uni- 
axial  material  which  Bertrand  had  taken  for  calcite  was  in 
reality  thaumasite,  and  Bertrand  in  a  letter  to  Nordenskioldf 
withdrew  his  objection.  He  gives  also  the  approximate 
indices  of  refraction  &>  =  1.503,  e  =  1.467,  which  differ  from 
those  of  calcite. 

In  1890  Widman  §  described  specimens  of  thaumasite 
belonging  to  the  mineral  collection  of  the  University  of 
Upsala,  which  are  reported  to  have  been  found  at  Kjolland, 
about  thirteen  miles  from  the  original  locality  Areskuta,  and 
two  analyses  by  Hedstrom  quoted  by  him  agree  very  closely 
with  the  ones  made  by  Lindstrom.  From  Hedstrom's  analy- 
ses the  formula  CaSiO3 .  CaCO3 .  CaSO4 . 15H2O  was  derived, 
and  as  pointed  out  by  Widman  this  slight  change  in  the 
formula  agrees  satisfactorily  with  the  analytical  results  of  Lind- 
strom, who  really  had  found  over  fourteen  and  one-half  mole- 
cules of  water. 

It  is  with  pleasure  that  the  authors  are  able  to  announce 
the  discovery  of  this  unusually  interesting  mineral  at  Burger's 

*  Geol.  For.  Fordhandl.,  Stockholm,  vol.  v,  p.  270,  1880. 

t  Geol.  For.  Forhandl.,  Stockholm,  vol.  ix,  p.  35,  1887. 

J  Ibid.,  vol.  ix,  p.  131, 1887.  §  Ibid.,  vol.  xii.,  p.  20,  1890. 


f 
248  OCCURRENCE   OF  THAUMASITE 

quarry,  West  Pater  son,  New  Jersey,  the  material  having  been 
first  brought  to  our  notice  by  Mr.  Geo.  L.  English,  of  New 
York,  who  sent  a  specimen  of  it  to  the  mineralogical  labora- 
tory of  the  Sheffield  Scientific  School  for  identification.  The 
mineral  occurs  as  an  aggregate  of  prismatic  crystals,  sometimes 
so  loosely  held  together  that  the  individuals  can  be  separated 
by  crushing  between  the  fingers,  while  more  often  the  masses 
are  firm  and  have  somewhat  the  appearance  of  white  alabaster. 
Occasionally  distinct  prismatic  crystals  were  observed,  aver- 
aging 0.5  mm.  in  diameter  and  2  to  4  mm.  in  length,  but  they 
were  poorly  formed  and  without  distinct  terminations.  Some 
of  the  masses  showing  fine  prismatic  crystals  have  a  decidedly 
silky  luster.  There  is  a  distinct  prismatic  cleavage.  Measure- 
ments were  only  possible  in  the  prismatic  zone  and  approxi- 
mated to  60°,  which  determine  the  crystallization  as  hexagonal. 
On  examining  fragments  imbedded  in  Canada  balsam  ones  can 
readily  be  found  which  show  a  uniaxial  interference  figure 
with  negative  double  refraction.  Using  a  polished  plate,  the 
index  of  refraction  for  the  ordinary  ray  was  determined  by 
means  of  total  reflection  in  a-mono-bromnaphthalene  and 
found  to  be  1.5125  for  yellow,  Na.  By  means  of  a  prism  of 
32°  58'  the  following  values  were  also  obtained  for  yellow, 
&)  — 1.519  and  e  — 1.476.  It  must  be  stated,  however,  that  a 
prism  cut  from  a  crystalline  aggregate  cannot  yield  wholly 
satisfactory  results,  as  the  light  does  not  traverse  a  single 
individual,  and  that  for  example  which  yielded  the  extraor- 
dinary value  above  was  vibrating  in  crystals  whose  vertical 
axes  were  approximately  and  not  perfectly  parallel  to  the 
edge  of  the  prism.  Levy  and  Lacroix*  give  &>  =  1.507  and 
e-1.468. 

In  order  to  be  absolutely  sure  of  the  uniform  character  of 
the  material  for  analysis,  selected  pieces  of  the  mineral  were 
crushed  and  sifted  to  a  uniform  grain  and  separated  by  means 
of  methyl  iodide,  CH3I,  which  was  diluted  with  ether.  That 
every  particle  of  the  mineral  in  the  separator  floated  at  a 
specific  gravity  of  1.887  and  sank  at  1.875,  a  difference  of  only 

*  Les  Mineraux  des  Roches,  p.  286,  1888. 


AT   WEST  PATERSON,  N.  J.  249 

0.012,  is  sufficient  proof  of  the  homogeneous  character  and 
great  purity  of  the  material.     Lindstrom  gives  as  the  specific 
gravity  of  the  Swedish  mineral  1.877  and  Widman  gives  1.83. 
The  results  of  the  analysis  are  as  follows : 

I.  II.  III.  Average.  Ratio. 

Si02  9.23  9.33          9.23  9.26  0.155          0.97 

C02  6.87  6.77         .  .  .  6.82  0.155          0.97 

S03  13.56  13.32         .  .  .  13.44  0.168          1.05 

CaO  .  .  .  27.08        27.19  27.13  0.484          3.04 

H20  42.81  42.72          .  .  .  42.77  2.377        15.00 

Na20  0.39         0.39  

K20  0.18         0.18  

99.99 

The  ratio  of  SiO2 :  CO2:  SO3:  CaO:  H2O  is  very  nearly 
1:1:1:3:  15,  demanded  by  the  formula  CaSiO3  .  CaCO3  . 
CaSO4  .  15H2O.  The  analytical  results  are,  moreover,  very 
close  to  those  obtained  upon  the  Swedish  mineral  by  Lindstrom 
and  Hedstrom.  A  slight  amount  of  alkali  sulphate  is  prob- 
ably present  as  impurity,  therefore  the  alkalies  have  been  neg- 
lected in  making  the  above  calculation.  That  Na2O  and  K2O 
are  not  isomorphous  with  CaO  is  shown  by  the  following  ex- 
periment :  1.1765  grams  of  the  powdered  mineral  were  treated 
in  a  platinum  dish  for  over  two  days  with  cold  water,  the 
insoluble  mineral  was  then  filtered  off  and  the  soluble  portion 
analyzed,  with  the  following  results :  SiO2,  0.39  per  cent ; 
SO8,  0.56  ;  CaO,  0.56 ;  Na2O  +  K4O,  0.25.  These  indicate  that 
thaumasite  is  slightly  soluble  and  that  the  alkalies  have  an 
independent  existence,  for  a  quantity  of  Na2O  -f-  K2O  equal  to 
about  one-half  of  that  found  in  the  original  analysis  was  ex- 
tracted, while  relatively  only  a  very  small  proportion  of  the 
calcium  was  dissolved,  a  result  which  would  not  have  taken 
place  if  the  alkalies  had  belonged  with  the  thaumasite.  A 
small  quantity  of  alkali  sulphate  may,  therefore,  he  regarded 
as  impurity,  and  deducting  from  the  analysis  the  alkalies  and 
sufficient  SO8  (0.64  per  cent)  to  convert  them  into  sulphates, 
and  recalculating  to  one  hundred  per  cent,  the  following  results 


250 


OCCURRENCE   OF  THAUMASITE 


are  obtained,  which  agree  satisfactorily  with  the  values  required 
by  theory : 


By  recalculation. 

Theory. 

Si02 

9.38 

9.64 

C02 

6.90 

7.08 

S03 

12.95 

12.86 

CaO 

27.47 

27.01 

H20 

43.30 

43.41 

100.00 


100.00 


Hoping  to  obtain  data  concerning  the  constitution  of  the 
mineral,  experiments  were  made  to  determine  the  temperature 
at  which  the  water  was  driven  off.  As  determined  by  Lind- 
strom,  the  mineral  slowly  loses  water  at  100°  C.,  and  in  our 
experiment,  after  heating  for  over  ninety  hours,  a  loss  of  29.35 
per  cent  was  obtained,  but  the  weight  had  not  become  con- 
stant. At  150°  the  weight  soon  became  constant  and  then  at 
200°,  250°  and  300°,  respectively,  constant  weights  were 
obtained,  and  in  each  case  the  heating  was  continued  until  the 
loss  of  weight  during  several  hours  did  not  amount  to  more 
than  a  few  tenths  of  a  milligram.  Between  300°  and  360° 
no  loss  of  weight  was  obtained,  but  the  material  still  contained 
water  which,  as  seen  by  a  closed  tube  experiment,  was  expelled 
at  much  below  a  red  heat. 

The  results  obtained  from  0.6663  gram  of  the  air-dry  min- 
eral are  as  follows : 


Two  days  in  desiccator 
Nine  hours  at  150° 
Seven  hours  at  200° 
Eight  hours  at  250° 
Five  hours  at  300° 
Below  redness 
Total 


Proportional  parts 
Loss.          using  T*5  of  total 
H20  as  unity. 

Nothing 
37.41 

13.13 

1.82 

0.64 

1.41 

0.50 

1.05 

0.37 

1.08 

0.38 

42.77 

It  is  evident  from  the  above  that  13  molecules  are  to  be  re- 
garded as  water  of  crystallization  and  two  molecules,  sufficient 


AT  WEST  PATERSON,  N.  J.  251 

to  form  four  hydroxyls,  as  constitutional.  The  last  two  mole- 
cules are,  moreover,  expelled  at  four  separate  temperatures, 
indicating  the  existence  of  four  hydroxyls  which  play  differ- 
ent parts  or  have  different  positions  in  the  molecular  structure. 
It  is  evident  also  that  the  CaSiO3,  CaCO8,  and  CaSO4,  together 
with  the  water,  are  united  in  some  way  into  a  complex 
molecule,  and  probably  as  suggested  by  Groth  *  in  some  way 
analogous  to  the  combination  of  silicate  and  sulphate  in  the 
haiiyne-nosean  group  of  minerals  or  of  silicate  and  carbonate 
in  cancrinite.  Regarding  silica  as  the  linking  non-metallic 
element,  the  following  constitution  may  be  suggested  as  a 

possible  one  : 

O 

HO-Ca-0_  0-C-O-Ca-OH 

HO>Sl<0-S-0-Ca-OH  '13H2° 


O     0 

The  above  may  also  be  expressed  as  [(CaOH)CO2]  [(CaOH) 
SO3]  [CaOH]  HSiO4  .  13H2O.  The  formula  agrees  in  a  very 
satisfactory  manner  with  the  results  obtained  by  driving  out 
the  water,  for  it  demands  four  independent  and  different 
hydroxyl  molecules.  Formulae  may  also  be  written  with  four 
hydroxyls  and  with  either  carbon  or  sulphur  as  the  linking 
element,  but  they  do  not  seem  to  the  authors  so  probable  as 
the  one  given  above. 

The  occurrence  of  thaumasite  at  Paterson  is  in  the  trap 
which  has  been  quarried  for  road  material.  It  is  associated 
with  heulandite,  apophyllite,  laumontite,  pectolite,  chabazite, 
scolecite  and  natrolite,  all  of  which  are  found  at  the  locality 
in  beautiful  crystals.  Widman  mentions  the  occurrence  of 
apophyllite  with  the  thaumasite  at  Kjb'lland.  The  thaumasite 
has  crystallized  later  than  the  zeolites  and  occurs  upon  or 
surrounding  them.  A  considerable  quantity  of  it  was  found, 

In  closing,  the  authors  desire  to  express  their  thanks  to 
Messrs.  Geo.  L.  English  &  Co.  of  New  York  for  generously 
furnishing  them  with  material  for  the  investigation. 

*Tabellarische  Uebersicht  der  Mineralien,  p.  149,  1889. 


ON  PEARCEITE,  A  SULPHARSENITE   OF  SILVER. 

BY  S.  L.  PENFIELD.* 
(From  Amer.  Jour.  Sci.,  1896,  vol.  2,  pp.  17-29.) 

THE  mineral  to  be  described  as  pearceite  in  the  present  arti- 
cle is  a  sulpharsenite  of  silver,  Ag9AsS6  or  9Ag2S  .  As2S3, 
analogous  to  polybasite  Ag9SbS6,  and  like  the  latter  charac- 
terized by  having  a  part  of  the  silver  replaced  by  copper  and 
often  by  small  quantities  of  zinc  and  iron.  It  cannot  be 
claimed  to  be  strictly  a  new  mineral,  for  as  an  arsenical  variety 
of  polybasite  it  has  previously  been  recognized,  although  no 
special  name  has  been  assigned  to  it.  H.  Rosef  first  de- 
scribed polybasite  and  gave  the  name  to  the  species  in  1828, 
and  in  1833  he  published  J  an  analysis  of  a  specimen  from 
Schemnitz  containing  arsenic,  with  only  a  trace  of  antimony, 
while  in  the  original  polybasite  from  Durango,  Mexico,  de- 
scribed by  him,  both  antimon}-  and  arsenic  were  present,  and 
he  recognized  the  fact  that  these  elements  were  isomorphous 
and  could  mutually  replace  one  another.  The  polybasites  from 
Durango  in  Mexico,  Freiberg  in  Saxony,  Pribram  in  Bohemia, 
the  Two  Sisters'  mine  near  Georgetown,  the  Yankee  Boy 
mine  near  Ouray,  and  the  Sheridan  mine  near  Telluride  in 
Colorado,  the  Comstock  Lode  in  Nevada,  and  apparently  from 
most  localities,  are  essentially  the  antimony  variety,  and  in 
mineralogical  literature  the  composition  of  polybasite  is  usu- 
ally given  as  a  sulphantimonite  of  silver.  Rammelsberg  § 
gives  an  analysis  by  Joy  of  polybasite  from  Cornwall,  Eng- 
land, where  antimony  and  arsenic  are  present  in  about  equal 
molecular  proportions,  and  the  author  in  connection  with 
Mr.  Stanley  H.  Pearce,  has  published  ||  analyses  of  arsenical 

*  A  portion  of  this  paper  treating  of  the  Crystallization  of  Polybasite  is 
here  omitted.  —  EDITOR. 

t  Fogg.  Ann.,  xv,  p.  573, 1829.  J  LOG.  cit.,  xxviii,  p.  56,  1833. 

§  Mineralchenrie,  p.  102,  1860.  ||  Amer.  Jour.  Sci.,  1892,  vol.  44,  p.  15. 


PEARCEITE,  A   SULPHARSENITE   OF  SILVER.       253 

polybasite  (pearceite)  from  the  Mollie  Gibson  mine,  Aspen, 
Colorado.  This  latter  material  was  not  distinctly  crystallized, 
but  was  found  in  great  quantity  and  was  the  mineral  which 
carried  the  bulk  of  the  silver  in  the  most  productive  silver 
mine  in  Colorado  at  that  time. 

The  author's  attention  has  recently  been  called  to  the  occur- 
rence of  beautifully  crystallized  pearceite,  or  arsenical  poly- 
basite from  the  Drumlummon  mine,  Marysville,  Lewis  and 
Clarke  Co.,  Montana.  The  mineral  was  first  sent  by  Mr.  R. 
F.  Bayliss,  of  the  Montana  Mining  Co.,  to  Dr.  Richard  Pearce, 
of  Denver,  with  the  request  that  it  should  be  investigated,  and 
the  following  analysis  was  made  by  Mr.  F.  C.  Knight  under 
Dr.  Pearce's  immediate  supervision. 

Found.  Ratio.  Theoretical  composition  where 

Ag2  :  Cu2  :  Fe  —  255  :  143  :  19. 

S  17.71-    32  =  0.553  11.95                 17.96 

As            7.39-    75  =  0.098  2.11  7.02 

Ag  55.17  -  216  =  0.255  \  55.61 

Cu  18.11  -127  =  0.143  V- 0.417  9.00                 18.34 

Fe            1.05-    56  =  0.019)  1.07 
Insol.      0.42 


99.85  100.00 

Dr.  Pearce  recognized  that  the  mineral  belonged  to  the  poly- 
basite class,  where  arsenic  played  the  role  usually  taken  by 
antimony,  and  forwarded  the  specimens,  together  with  the 
analysis,  to  the  author  for  an  expression  of  opinion.  As  may 
be  seen  from  the  ratio,  the  proportion  of  S  :  As :  (Ag2  +  Cu2  + 
Fe)  is  very  nearly  12 :  2 :  9,  which  is  that  demanded  by  the 
polybasite  formula,  and  taking  the  metals  in  the  same  propor- 
tion as  they  are  found  in  the  analysis,  Ag2 :  Cu2 :  Fe  =  255 : 
143:  19,  and  calculating  the  theoretical  composition,  results 
agreeing  very  satisfactorily  with  the  analysis  are  obtained. 

Although  recognizing  that  antimony  and  arsenic  are  isomor- 
phous  and  may  mutually  replace  one  another,  it  is  customary 
and  has  been  found  convenient  in  mineralogy  to  consider  the 
sulphantimonites  and  sulpharsenites  as  distinct  species,  and 
to  designate  them  by  different  names,  and  the  author  proposes 


254      PEARCEITE,  A    SULPHARSENITE   OF  SILVER. 

that  hereafter  the  name  polybasite  shall  be  restricted  to  the 
antimony  compound  Ag9SbS6,  and  to  make  of  the  correspond- 
ing arsenic  compound,  Ag9AsS6,  a  distinct  species.  For  the 
arsenical  mineral  he  takes  pleasure  in  proposing  the  name 
pearceite  as  a  compliment  to  his  friend,  Dr.  Richard  Pearce,  of 
Denver,  whose  keen  interest  in  mineralogy  and  connection 
with  one  of  the  large  smelting  and  refining  works  of  Colorado 
have  made  him  known  alike  to  scientific  men  and  to  those 
interested  in  the  development  of  the  mining  industries  of  the 
Rocky  Mountain  region.  The  author  furthermore  takes  plea- 
sure in  expressing  his  thanks  to  Mr.  Bayliss,  who  has  taken 
a  great  interest  in  the  investigation  and  naming  of  the  mineral, 
and  has  most  generously  placed  at  his  disposal  all  of  the  avail- 
able material. 

It  seems  best  to  give  at  this  point  the  analyses  of  pearceite, 
already  referred  to,  which  have  previously  been  published  as 
arsenical  varieties  of  polybasite.  In  the  theoretical  composi- 
tion given  with  each  the  ratio  of  the  metals  is  the  same  as  in 
the  accompanying  analysis. 

I.   H.  Rose,  Ag2 :  Cu2  :  Zn  :  Fe  =  335  :  24  :  9  :  6. 
II.   Penfield,    after    deducting  12.81    per    cent   of    impurities, 

mostly  PbS,  Ag2  :  Cu2 :  Zn  =  263  :  117  :  43. 
III.   S.  H.  Pearce,  after  deducting  28.18  per  cent  of  impurities, 
mostly  PbS,  Ag2 :  Cu2  :  Zn  =  276  :  102  :  49. 

II.  III.  Theory  for 


S 
As 

Sb 

Scheinnitz. 

16.83 
6.23 
0.25 

Theory. 

16.19 
6.32 

Aspen,  Colo. 

18.13 
7.01 
030 

Theory. 

18.13 
7.08 

Aspen. 

17.73 

6.29 
0.18 

Theory. 

18.02 
7.03 

AgflAsS6. 

15.50 
6.05 

Ag 
Cu 
Zn 
Fe 

72.43 
3.04 
0.59 
0.33 

73.47 
3.08 
0.60 
0.34 

56.90 
14.85 
2.81 

57.07 
14.91 
2.81 

59.73 
12.91 
3.16 

59.06 
12.77 
3.12 

78.45 

99.70 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

PEARCEITE,  A    SULPHARSENITE   OF  SILVER.       255 

Crystallization. 

The  crystallization  of  pearceite  is  monoclinic  but  with  a  close 
approximation  to  rhombohedral  symmetry.  The  habit  is  com- 
monly hexagonal  with  the  basal  planes  prominent  and  the 
zones  of  bevelling  forms  between  them  often  highly  modified. 
The  material  from  which  crystallographic  data  could  be  ob- 
tained came  wholly  from  a  single  specimen  where  the  crystals 
were  implanted  upon  a  gangue  of  quartz  and  imbedded  in  cal- 
cite,  and  were  obtained  by  dissolving  the  latter  in  dilute  acid. 
Unfortunately  the  crystals  had  grown  close  together,  thus 
interfering  more  or  less  with  another,  and  they  also  were 
cracked,  probably  owing  to  the  severe  shocks  received  in  the 
processes  of  blasting  and  mining  ;  consequently  when  liberated 
by  dissolving  the  calcite  they  fell  to  pieces,  so  that  usually 
only  parts  of  crystals  were  available  for  measurement.  The 
faces  had  a  beautiful  metallic  luster,  and  when  free  from  stria- 
tions  and  vicinal  planes  gave  excellent  reflections  on  the  gonio- 
meter. The  determination  of  the  crystalline  form  and  the 
axial  ratio  proved  to  be  a  difficult  matter  owing  to  the  frag- 
mentary character  of  the  crystals,  their  grouping,  often  in 
nearly  parallel  position,  a  probable  twinning,  and  their  close 
approximation  to  rhombohedral  symmetry,  and  it  was  not 
until  many  measurements  had  been  made  upon  a  series  of  crys- 
tals that  a  satisfactory  solution  of  the  problem  was  obtained. 

As  fundamental  measurements,  the  following  were  selected : 

m  A  m,  110  A  T10  =  60°  2' 
c  A  d,  001  A  102  =  25°  3' 
c  A  a,  001  A  100  =  89°  51' 

from  which  the  axial  ratio  was  calculated  : 

a:  b:  c  =  1.7309  :  1  :  1.6199; 
(3  =  001  A  100  =  89°  51' 

The  crystals  are  quite  highly  modified,  and  it  seems  best 
before  giving  a  list  of  the  forms  to  explain  the  different  kinds 
which  were  observed  and  to  state  something  concerning  their 


256      PEARCEITE,  A   SULPHARSENITE   OF  SILVER. 

occurrence.  The  basal  pinacoid  c  (001)  is  prominent,  is  hex- 
agonal or  triangular  in  shape,  and  is  characterized  by  triangular 
markings  and  vicinal  planes,  Figure  1,  so  that  it  was  often  im- 
possible to  obtain  accurate  measurements  from  it.  The  prism 
ra  (110)  and  the  pinacoid  a  (100)  are  nearly  at  right  angles  to 
cand  60°  from  one  another,  so  that  the  combination  approaches 
very  closely  to  a  hexagonal  prism,  and  it  is  sometimes  impos- 
sible to  disiinguish  a  from  m,  or,  without  accurate  measure- 
ments, to  decide  whether  the  forms  between  e  and  a  or  c  and  m 
modify  the  acute  or  obtuse  angles.  It  is  very  probable  that  a 
twinning  is  present,  similar  to  that  of  the  micas  and  chlorites, 
where  the  twinning  plane  is  at  right  angles  to  c  in  the  zone 
m  A  c,  and  where  the  parts  are  superimposed  upon  one  another 
with  c  as  the  composition  face,  but  no  absolute  proof  of  this 
was  obtained.  The  crystals  are  opaque,  so  that  optical  tests 
could  not  be  applied  as  was  done  by  Miers,*  who  has  described 
this  kind  of  twinning  on  polybasite.  If  the  twinning  occurs 
on  pearceite,  as  it  probably  does,  it  must  cause  uncertainty  as 
to  the  identification  of  some  of  the  forms  in  the  zones  between 
c  and  a  and  c  and  m,  and  it  may  also  account  in  part  for  the 
decidedly  rhombohedral  aspect  of  many  of  the  crystals.  As 
far  as  could  be  observed,  similar  faces  are  often  developed 
about  equally  above  and  below  m  and  a  in  the  zones  between 
the  basal  planes,  but  to  what  extent  this  is  due  to  twinning  it 
is  impossible  to  state.  The  faces  in  these  zones  are  moreover 
commonly  striated  parallel  to  their  mutual  intersection,  and 
while  r  and^>,  r°  ancl^>°,  n  and  t  and  n°  and  t°  (compare  Fig- 
ure 1  and  the  list  of  forms  beyond),  are  the  most  prominent, 
other  faces,  especially  e  and  e°,  f  and  /°,  s  and  s°  and  u  and  u°, 
are  very  often  present.  When  q  was  observed  it  was  always  a 
prominent,  dull  face,  not  sharing  in  the  horizontal  striations  of 
the  other  faces  of  the  zone.  It  was  only  occasionally  that 
forms  were  observed  between  c  (001)  and  I  (310)  and  they 
were  always  small,  while  the  corresponding  forms  were  not 
observed  between  (001)  and  (310).  The  pinacoid  I  (010) 
was  identified,  not  only  by  the  symmetrical  arrangement  of 

*  Min.  Mag.,  viii,  p.  204,  1889. 


PEARCEITE,  A    SULPHARSENITE   OF  SILVER.       257 

the  forms  with  reference  to  it,  but  also  by  the  similarity  of  the 
angles  measured  from  it  on  to  similar  adjacent  forms.  The 
prism  I  (310)  is  often  developed  about  equal  in  size  to  &,  and 
with  the  latter  would  correspond  in  rhombohedral  symmetry 
to  a  hexagonal  prism  of  the  second  order.  The  prism  h  (130) 
and  the  clino-dome  k  (021)  were  found  together  on  only  one 
crystal  as  small  faces  symmetrically  located  with  reference 
to  the  pinacoid  b. 


FIGURE  1. 

Figure  1  shows  the  prevailing  type  of  crystal,  with  hex- 
agonal aspect,  the  characteristic  triangular  markings  on  the 
basal  plane,  but  with  only  the  most  prominent  of  the  bevel- 
ling faces  present.  Two  fragments  were  found  which  in  habit 
were  essentially  like  Figure  2.  These  had  a  decidedly  mono- 
clinic  habit  and  were  the  most  free  from  striations,  vicinal 
faces  and  indications  of  a  possible  twinning  of  any  crystals 
that  were  observed,  and  from  them  the  fundamental  measure- 
ments previously  given  were  obtained. 

A  few  crystals  were  quite  remarkable  for  their  size,  the  hex- 
agonal plates  being  3  cm.  in  diameter  and  1  cm.  thick,  but  they 
were  coated  with  drusy  quartz  and  could  not  be  used  for  crys- 
tallographic  measurement.  The  specimen  showing  the  largest 
crystals  was  presented  by  Mr.  Bayliss  to  the  author  for  the 
Brush  collection  at  New  Haven.  The  crystals  from  which 
the  measurements  were  obtained  averaged  less  than  4  mm.  in 
diameter. 

The  following  list  includes  the  forms  which  have  been 
observed,  but,  as  already  stated,  twinning  may  account  for  a 
similar  form  being  found  modifying  both  the  acute  and  obtuse 
angles  of  the  crystals  and  being  repeated  in  the  zones  between 
c  and  a  and  c  and  m. 

17 


258       PEARCEITE,  A    SULPHARSENITE   OF  SILVER. 

a,  100  d,  102  t°,  201  s,  221  s°,  221 

b,  010  n,  101  «°,  501  M,  331  u°,  331 

c,  001  *,  201  /°,  601  o°,  T14  x,  311 
I,  310  e,  401  o,  114  gr°,  T13  y,  313 
m,  110  /,  601  r,  112  r°,  T12  «,  3.1.12 
ft,  130  4  203  p,  111  j»°,  Til 

A;,  021    n°,  T01    v,  332    v°,  332 

The  forms  corresponding  to  these,  found  by  Miers*  on 
polybasite,  are  c,  m,  w,  £,  /?,  s,  r,  and  to  (109). 

The  following  table  of  measured  angles  includes  a  series 
which  was  selected  wholly  on  account  of  the  character  of  the 
reflections,  due  to  the  freedom  of  the  faces  from  striations  and 
other  disturbing  influences.  They  were  mostly  made  on  the 
two  fragmentary  crystals,  already  mentioned,  having  a  habit 
like  Figure  2,  and  where  several  measurements  are  given  they 

Calculated.  Measured. 

c  A  a,  001  A  100  89°  51'  89°  51'  f    89°  49' 

c  A  I,  001  A  310  89°  52'     89°  48'     89°  54' 

c  A  m,  001  A  110  89°  55i'    89°  55' 

m  A  m,  110  A  T10  60°  2'     60°  2'  f 

b  A  m,  010  A  110  30°  1'     30°  1'     30°  1' 

a  A  I,  100  A  310  29°  59'     29°  58'     29°  57 J' 

b  A  h,  010  A  130  10°  54'     10°  53' 

b  A&,  010  A  021  17°  9'     17°  5' 

c  A  d,  001  A  102  25°  3'     25°  3f     25°  2 J' 

c  A  n,  001  A  101  43°  2'     43°  4'     43°  5' 

c  A  e°,  001  A  40T  104°  49'  104°  53^' 

c  A  *°,  001  A  20T  118°  00'  117°  56' 

c  A^°,001  A  10T  136°  49£'  136° 


c  Ar,  001  A  112  43°  3'  43°  3'     TT0  ^ 

c  Ap,  001  A  111  61°  49'  61°  56' 

J  A  r,  102  A  112  36°  14'  36°  12'     36°  16' 

b  A  p,  010  A  111  40°  15'  40°  12'     40°  12' 

b  Ajp°,  010  A  Til  40°  10J'  40°  8' 

b  AS,  010  A  221  33°  12'  33°  12' 

c   A  y,   001  A  313  47°    9'  47°  10'  47°    7' 

*  Loc.  cit.  t  Fundamental  measurements. 


PEARCEITE,  A    SULPHARSENITE   OF  SILVER.       259 

represent  independent  ones  in  different  zones  or  on  different 
crystals.  As  may  be  seen,  the  measured  angles  show  a  fairly 
good  agreement  with  the  calculated  values,  and  it  may,  there- 
fore, be  assumed  that  the  axial  ratio  has  been  determined 
with  a  high  degree  of  accuracy. 

In  the  following  table  the  calculated  angles  of  most  of  the 
faces  on  to  the  basal  plane  are  given,  arranged  so  as  to  show 
the  slight  variation  from  one  another  and  from  rhombohedral 
symmetry  of  the  forms  d,  o  and  o°  ;  A  and  q°  ;  n,  r,  n°  and 
r°  ;  t,  p,  t°  and  p°  ;  v  and  v° ;  e,  «,  e°  and  s°  and/,  u,  f° 
and  u°. 

c  A  d    =  25°    3'  c  A  n°  -  43°  10|'  CAW    =70°  19'  c  A/    =  79°  45' 

c  A  o    =  25°  3'  c  A  r°  =  43°    l\f  c  A  v°  =  70°  27'  CAM    =  79°  49^ 

c  A  o°  -  25°  4£'  c  A  t     -  61°  46 1'  c  A  c    =74°  54'  c  A/°  =  80°    2' 

c  A  A   =  32°  0'  c  A  p    =  61°  49'  CAS    =  75°  00'  c  A  w°  =  79°  58' 

c  A  7°  =  31°  58'  CA*°  =62°  00'  cAe°=75°ll/  CAZ    =15°    6J' 

c  A  n    =  43°  2'  c  A  p°  =  61°  56'  c  A  s°  =  75°    6'  c*y=  47°    9' 

c  A  r    -  43°  3'  c  A  x    -  72°  44' 

Physical  properties.  —  Pearceite  is  brittle,  has  an  irregular 
to  conchoidal  fracture  and  no  distinct  cleavage.  The  hardness 
is  about  3.  The  specific  gravity  was  taken  with  a  chemical 
balance  on  three  different  portions  of  carefully  selected  mate- 
rial and  gave  6.125,  6.160  and  6.166,  the  mean  of  these  being 
6.15.  The  luster  is  metallic  and  the  color  of  the  mineral  and 
the  streak  is  black.  The  material,  even  in  thin  particles,  is 
opaque.  In  the  ruby  silvers  the  arsenical  compound  proustite 
is  more  transparent  than  the  antimony  one  pyrargyrite,  and  we 
might,  therefore,  naturally  expect  pearceite  to  be  more  trans- 
parent than  polybasite,  but  that  this  is  not  the  case  may  be 
due  to  the  fact  that  the  variety  of  pearceite  under  examination 
contains  over  18  per  cent  of  copper,  while  the  published 
analyses  of  polybasite  indicate  usually  about  5  and  never  over 
10  per  cent  of  this  element. 

Pyrognostics  and  other  tests.  —  Before  the  blowpipe,  pearce- 
ite decrepitates  slightly  and  fuses  at  about  one.  Heated  on 
charcoal  in  the  oxidizing  flame,  a  slight  coating  of  As2O3  is 
formed  and  by  addition  of  borax  or  sodium  carbonate  and  con- 


260       PEARCEITE,  A    SULPHARSENITE   OF  SILVER. 

tinned  heating  a  globule  of  metallic  silver  is  obtained.  In  the 
open  tube  SO2  is  given  off  and  a  volatile  sublimate  of  As2O3  is 
formed.  In  the  closed  tube  the  mineral  fuses,  yields  a  yellow 
sublimate  of  sulphide  of  arsenic  and  above  the  latter  a  very 
slight  one  of  sulphur.  The  powder  is  readily  oxidized  and 
dissolved  by  nitric  acid.  The  solution  yields  with  hydrochloric 
acid  an  abundant  precipitate  of  silver  chloride  and  on  addition 
of  ammonia  in  excess  the  blue  color  characteristic  of  copper  is 
obtained,  while  a  slight  precipitate  of  ferric  hydroxide  is 
formed. 

Occurrence.  —  According  to  information  received  from  Mr. 
Bayliss,  the  pearceite  crystals  were  found  with  quartz  and 
calcite  lining  a  vug  at  only  one  place  in  the  Drumlummon 
mine,  and  although  a  diligent  search  has  been  made  for  similar 
crystals  in  other  parts  of  the  mine  none  have  been  found.  A 
few  chalcopyrite  crystals  were  observed  intimately  associated 
with  the  pearceite.  High  grade  silver  and  gold  ores  are  taken 
from  the  Drumlummon  mine,  and  on  one  of  the  specimens  of 
the  ore  argentiferous  tetrahedrite,  freibergite,  was  observed. 


ON  NORTHUPITE;    PIRSSONITE,    A  NEW   MINERAL; 

GAY-LUSSITE  AND  HANKSITE  FROM  BORAX  LAKE, 

SAN  BERNARDINO  COUNTY,   CALIFORNIA. 

BY  J.  H.  PRATT  * 
(From  Amer.  Jour.  Sci.,  1896,  vol.  2,  pp.  123-135.) 

INTRODUCTION. 

THE  minerals  to  be  described  in  this  paper  are  from  the 
remarkable  locality  of  Borax  Lake,  San  Bernardino  County, 
California.  They  were  brought  to  the  author's  notice,  in  the 
fall  of  1895,  by  Mr.  Warren  M.  Foote  of  Philadelphia,  who 
sent  one  of  them,  the  northupite,  together  with  some  of  the 
associated  minerals,  to  the  mineralogical  laboratory  of  the 
Sheffield  Scientific  School,  for  chemical  investigation.  About 
the  same  time  Mr.  C.  H.  Northup  of  San  Jose*,  Cal.,  sent  some 
minerals  from  the  same  region  to  Prof.  S.  L.  Penfield.  Among 
them,  gay-lussite,  hanksite  and  a  third  mineral,  which  has 
proved  to  be  a  new  species,  were  identified.  These  same 
minerals  were  also  observed  among  the  specimens  sent  by  Mr. 
Foote.  Mr.  Northup,  in  his  letter  of  transmittal,  stated  that 
he  had  carefully  saved  all  the  crystals  of  the  new  mineral, 
having  observed  that  they  were  different  from  gay-lussite  in 
habit,  and  that  he  believed  they  would  prove  to  be  a  new  and 
interesting  species. 

Both  Mr.  Northup  and  Mr.  Foote  have  thus  most  gener- 
ously furnished  material  for  this  investigation,  and  the  former 
has  also  supplied  valuable  information  concerning  the  locality 
and  mode  of  occurrence  of  the  minerals.  The  author,  there- 
fore, takes  great  pleasure  in  expressing  his  thanks  to  both  of 
these  gentlemen  for  the  services  they  have  rendered. 

*  The  tables  of  measured  and  calculated  angles  and  also  the  part  of  this 
paper  referring  to  gay-lussite  are  here  omitted.  —  EDITOR. 


262  MINERALS  FROM 

In  addition  to  the  investigation  of  northupite  and  the  new 
mineral,  some  interesting  data  concerning  hanksite  and  gay- 
lussite  have  also  been  obtained. 

Occurrence.  —  The  Borax  Lake  region  has  already  been 
described  by  De  Groot  *  and  Hanks  f  and  therefore  only  a 
brief  description  is  necessary  in  this  article. 

This  alkali  lake,  or  better,  alkali  marsh,  is  situated  in  the 
northwestern  corner  of  San  Bernardino  County  near  the  Inyo 
County  line  and  is  72  miles  from  Mojave,  the  shipping  point 
for  that  district.  Borax  Lake  proper  is  a  small  basin  about 
one  mile  and  a  half  in  length  by  half  a  mile  wide,  separated  by 
a  narrow  ridge  from  a  larger  basin,  which  is  about  ten  miles 
long  and  five  miles  wide,  known  as  "  Dry  Lake,"  "  Alkali 
Flat,"  "  Salt  Bed,"  and  "  Borax  Marsh."  The  appropriateness 
of  these  names  is  very  apparent,  for  the  marsh  is  really  a  dry 
lake,  partly  filled  up  with  salt,  borax,  alkali,  mud,  and  volcanic 
sand.  During  the  wet  seasons  a  little  water  accumulates,  but 
it  remains  only  a  short  time  and  is  never  over  a  foot  or  two 
deep,  while  in  most  places  it  is  not  more  than  two  or  three 
inches.  In  the  smaller  basin,  however,  the  water  stands  con- 
siderably longer.  The  larger  basin  is  somewhat  lower  than 
the  other,  the  narrow  ridge  referred  to  above  preventing  the 
waters  of  the  smaller  basin  from  flowing  into  it. 

At  the  present  time,  borax  is  the  only  product  manufactured 
from  the  minerals  of  the  locality,  and  it  is  from  the  smaller 
basin  and  the  narrow  ridge  that  most  of  it  is  obtained.  Tin- 
cal,  or  native  borax,  has  been  found  in  crystals  to  a  depth  of 
450  feet,  which  is  as  deep  as  explorations  with  drills  have 
penetrated.  "  Crude  borax  "  is  described  by  Mr.  Northup  as 
found  on  the  surface  of  the  higher  parts  of  the  lake,  in  a 
condition  resembling  burnt  bone.  Underlying  this  is  a  very- 
hard,  uneven  deposit  of  different  salts,  which  is  generally  not 
disturbed.  The  crude  borax  is  collected  only  to  a  depth 
varying  from  two  to  eight  inches,  although  the  original  thick- 
ness is  much  greater.  In  about  four  years,  the  efflorescence 

*  Report  State  Min.  of  Cal.,  1890,  p.  534. 
t  Amer.  Jour.  Sci.,  1889,  vol.  37,  p.  63. 


BORAX  LAKE,   CALIFORNIA.  263 

of  borax  forms  again,  the  solution  being  drawn  up  by  capillary 
attraction  and  leaving  the  bone-like  deposit  on  evaporation. 
Most  of  the  borax  is  obtained  from  this  crude  material, 
although  some  is  obtained  by  the  evaporation  of  the  natural 
solution  of  borax  in  the  lake  water. 

The  minerals  described  beyond  were  found  while  exploring 
the  underlying  formations,  and  were  obtained  by  Mr.  Northup 
after  carefully  working  over  the  tailings  or  de*bris  from  the 
borings. 

The  minerals  associated  with  the  borax  at  this  region  are, 
according  to  Hanks,*  sulphur,  gold,  cerargyrite,  embolite, 
halite,  anhydrite,  thenardite,  celestite,  glauberite,  gypsum,  cal- 
cite,  dolomite,  trona,  gay-lussite,  natron,  hanksite,  colemanite, 
tincal,  soda  niter  and  hydrosulphuric  acid.  To  this  list 
sulphohalite,  northupite  and  the  new  mineral  to  be  described 
in  this  paper  must  be  added.  Of  the  foregoing,  colemanite,! 
hanksite,  J  and  sulphohalite  §  were  first  derived  from  this 
locality. 

NORTHUPITE. 

A  preliminary  description  of  this  mineral  has  been  given  by 
Mr.  Warren  M.  Foote.||  According  to  information  received 
from  Mr.  Northup,  it  has  been  found  in  only  one  boring, 
known  as  the  "  New  Well,"  and  was  probably  formed  in  a 
stratum  of  clay,  about  450  feet  below  the  surface.  With  two 
exceptions,  northupite  has  been  observed  only  in  detached 
crystals,  Mr.  Foote  having  in  his  possession  a  single  specimen 
showing  two  octahedrons  of  northupite  attached  to  a  crystal 
of  the  new  mineral,  pirssonite,  to  be  described  beyond,  and  a 
similar  specimen  being  in  the  Brush  collection. 

Physical  properties.  —  The  crystallization  is  isometric,  the 
octahedron  being  the  only  form  observed.  The  crystals  vary 

*  Amer.  Jour.  Sci.,  1889,  vol.  37,  p.  66. 

t  Bull.  Cal.  Acad.,  No.  2,  Jan.,  1885,  and  Zeitschr.  Kryst,  10,  p.  179,  1884. 
t  Amer.  Jour.  Sci.,  1885,  vol.  30,  pp.  133  and  136 ;  also,  1889,  vol.  37,  p.  63. 
§  Ibid.,  1888,  vol.  36,  p.  463.    Also  this  volume,  p.  343. 
||  Proceedings  of  the  Acad.  of  Nat.  Sci.  Phil.,  Sept.  1895.    Also  Am.  Jour. 
Sci.,  1895,  vol.  50,  p.  480. 


264  MINERALS  FROM 

in  size  from  less  than  a  millimeter  to  rarely  a  centimeter  in 
diameter.  There  is  no  apparent  cleavage,  but  the  crystals, 
which  are  extremely  brittle,  break  with  a  distinct  conchoidal 
fracture.  The  luster  on  fractured  surfaces  is  decidedly 
vitreous.  The  hardness  is  between  3.5  and  4.  The  specific 
gravity  was  obtained  by  floating  the  crystals  in  methylen 
iodide  diluted  with  methyl  iodide  and  was  found  to  be  2.380. 
The  pure  material  is  colorless,  but  owing  to  impurities  the 
color  of  the  crystals,  as  stated  by  Foote,  varies  from  dirty 
white,  pale  yellow  and  greenish-gray  to  dark  brown.  The 
impurities  are  probably  clay  or  organic  matter  and  Foote  has 
called  attention  to  their  arrangement  in  directions  parallel  to 
the  axial  planes  of  the  isometric  system.  No  decomposition 
on  exposure  to  the  air  has  been  observed. 

Optical  properties.  —  Fragments  of  the  mineral,  when  exam- 
ined in  polarized  light,  were  found  to  be  isotropic.  By  means 
of  a  prism  of  79°  35'  the  following  indices  of  refraction  were 
determined : 

nr  =  1.5117  Li.        ny  =  1.5144  Na.        ngr.  =  1.5180  Tl. 

Chemical  composition.  —  A  qualitative  examination  showed 
the  presence  of  carbonic  acid,  chlorine,  sodium,  magnesium, 
and  minute  traces  of  sulphuric  acid  and  water.  Potassium 
was  very  carefully  tested  for,  but  not  even  a  trace  of  it  could 
be  detected. 

The  results  of  the  analyses  are  as  follows : 

I.  II.  Average.  Ratio. 

C02          35.21         35.02        35.12        0.798        2.01 
Cl  14.10  14.10        0.397        1.00 


S03  0.08          0.08          0.08         

MgO        15.96        16.20        16.08        0.402        1.01 
Na00       36.99         .  .  .         36.99        0.597        1.50 

H26  0.72         .  .  .  0.72         

Insol.        0.25          0.19          0.22 

103.31 
0  equivalent  to  Cl  3.16 

100.15 


BORAX  LAKE,   CALIFORNIA.  265 

The  ratio  of  the  CO2 :  Cl :  MgO  :  Na2O  is  almost  exactly 
2  :  1  :  1  :  1.5.  Two-thirds  of  the  sodium,  if  taken  to  form  a 
molecule  of  Na2CO3,  would  leave  just  enough  to  form  with 
the  chlorine  a  molecule  of  NaCl.  This  would  then  give  as 
the  formula,  MgCO3 .  Na2CO3 .  NaCl. 

The  percentage  composition  required  by  this  formula  is 
given  below,  together  with  the  results  of  the  analysis  recalcu- 
lated to  100  per  cent,  after  deducting  the  slight  amounts  of 
water  and  insoluble  material  and  converting  a  sufficient  amount 
of  the  soda  into  metallic  sodium  to  unite  with  the  chlorine 
and  form  NaCl. 

T*        ,  Calculated  for 

Found.  MgCO-a .  Na2C03 .  NaCl. 

C02     35.43  35.41 

MgO 16.22  16.09 

!STa2O     24.90  24.96 

Cl    ..."....  14.23  14.28 

Na 9.22  9.26 

100.00  100.00 

Pyrognostics.  —  Before  the  blowpipe,  the  mineral  fuses  at 
1,  with  frothing,  due  to  escaping  carbon  dioxide,  and  yields 
a  white  or  grayish  white  mass,  which  reacts  alkaline  with 
moistened  turmeric  paper.  The  flame  is  colored  intensely 
yellow.  In  the  closed  tube,  the  mineral  decrepitates  violently, 
sometimes  giving  off  a  trace  of  water,  derived  probably  from 
impurities  held  mechanically  in  the  crystals.  The  crystals 
are  easily  soluble  in  cold  dilute  hydrochloric  and  nitric  acids 
with  effervescence.  Cold  water  acts  slowly  on  the  mineral, 
but  hot  water  decomposes  it  very  rapidly  with  separation  of 
magnesium  carbonate. 

Name.  —  The  name,  northupite,  was  given  to  this  mineral 
by  Mr.  Foote  as  a  compliment  to  Mr.  Northup,  whose  very 
careful  search  has  brought  to  light  a  number  of  interesting 
minerals  from  this  locality. 

PmssoNiTE,  A  NEW  MINERAL. 

As  stated  in  the  introduction,  a  new  mineral  was  first 
observed  by  Mr.  Northup  among  some  crystals  of  gay-lussite, 


266 


MINERALS  FROM 


which  it  somewhat  resembles.  It  has  been  found  very  spar- 
ingly in  only  one  boring,  "  New  Well,"  which  also  furnished 
the  northupite  crystals.  With  the  two  exceptions  mentioned 
under  northupite,  only  detached  crystals  have  been  observed, 
and  they  were  probably  formed  in  the  same  part  of  the  de- 
posit which  yielded  the  northupite.  Unfortunately,  pirssonite 
must  be  classed  among  the  rare  minerals ;  but  it  is  hoped  that, 
as  explorations  are  carried  on,  it  will  be  found  in  other  parts 
of  the  deposit. 

Crystalline  form.  —  The  mineral  crystallizes  in  the  ortho- 
rhombic  system  and  is  hemimorphic  in  its  development.  The 
hemimorphic  axis  has  been  taken  as  the  vertical  one,  and  the 
forms  which  have  been  observed  are  as  follows : 


b,    010 
m,   110 


111 
11T 


e,   131 
x,  311 


The  axial  ratio,  derived  from  the  measurements  marked  by 
asterisks  in  the  table  beyond,  is  as  follows  : 

a  :  b  :  c  =  0.56615  :  1  :  0.3019 

Although  the  forms  are  not  numerous  the  crystals  show  a 
considerable  variety  in  habit.     Figures  1  and  2,  drawn  with 


FIGURE  1. 


FIGURE  2. 


FIGURE  3. 


010  in  front,  in  order  to  show  the  shape  better,  represent  the 
prevailing  types.  The  pyramid  e  is  developed  at  one  ex- 
tremity of  the  vertical  axis  only,  and  varies  much  in  size. 
Often  e  alone  terminates  the  upper  end  of  the  crystals,  Figures 
3  and  6.  The  pinacoid  b  is  sometimes  wanting  as  represented 
by  Figures  4  and  5.  The  pyramid  x  was  observed  on  only  a 


BORAX  LAKE,    CALIFORNIA. 


267 


single  fragmentary  crystal  and  is  not  represented  in  the  fig- 
ures. The  crystals  vary  much  in  size;  the  smaller  ones, 
averaging  about  5  mm.  in  greatest  diameter,  usually  have  the 
habit  represented  by  Figures  1  and  2 ;  while  the  larger  ones, 
sometimes  15  mm.  in  length,  are  usually  developed  like  Figures 
4  and  5.  The  larger  prismatic  crystals  are  often  only  well 
terminated  at  that  end  where  the  e  faces  occur. 


FIGURE  4. 


FIGURE  5. 


FIGURE  6. 


The  following  table  includes  a  list  of  the  measured  and  cal- 
culated angles.  As  the  reflections  were  not  always  very  per- 
fect, the  extremes  of  two  or  more  independent  measurements 
are  given: 


Measured. 

Mean. 

Calculated. 

p/\p" 

111  A  Til 

62°  57' 

-63°  3' 

*63°  0' 

m  A  w'" 

110  A  110 

59° 

-59°  4'  30" 

*59°  2' 

p  A  b 

111  AGIO 

74°  51' 

30"  -75°  7' 

75°  1'33" 

75°  5' 

P  A  TO 

111  A  110 

58°  32' 

-  58°  47' 

58°  38'  15" 

58°  30' 

PAP' 

111  A  111 

53°  57' 

-54°  5' 

53°  59'  36" 

54°  6' 

p  A  p'" 

111  A  111 

29°  54' 

-  29°  59'  30" 

29°  57'  30" 

29°  50' 

6  A  e 

010  A  131 

51°  14' 

-  51°  43' 

51°  26'  50" 

51°  22' 

e  A  e  '" 

131  A  181 

76°  56' 

-  77°  12' 

77°  4' 

77°  16' 

a:  A  *"' 

311  A  311 

18°  12' 

48" 

18°  12'  48" 

18°  10'  30" 

x  /\m 

311  A  110 

36°  44' 

-  36°  45' 

36°  44'  30" 

36°  15'  20" 

x  A  m'" 

311  A  110 

49°  26' 

-  49°  23' 

49°  24'  30" 

49°  24' 

Physical  properties.  —  The  crystals  are  extremely  brittle, 
breaking  with  a  conchoidal  fracture,  but  with  no  apparent 
cleavage.  The  luster  is  vitreous.  They  vary  from  colorless 
to  white,  but  are  often  darkened  by  impurities.  The  hardness 


268  MINERALS  FROM 

is  between  3  and  3.5.  The  specific  gravity,  taken  by  suspen- 
sion in  methylen  iodide,  was  found  to  be  2.352. 

The  crystals  exhibit  the  phenomenon  of  pyroelectricity  in  a 
marked  degree.  While  cooling,  after  being  gently  heated,  the 
extremity  upon  which  the  acute  pyramid  e  (131)  is  developed, 
became  negatively  electrified.  This  was  shown  by  dusting 
with  a  mixture  of  red  oxide  of  lead  and  sulphur,  as  recom- 
mended by  Kundt.* 

Optical  properties.  —  The  plane  of  the  optic  axes  is  the  base 
and  the  axis  b  is  the  acute  bisectrix.  The  optical  orientation 
is  a  —  #,  b  =  c  and  c  =  b.  The  double  refraction  is  positive 
and  strong.  The  dispersion  is  slight  p  <  v. 

For  the  determination  of  the  indices  of  refraction  the 
method  of  total  reflection  was  employed,  making  use  of  a 
crystal  upon  which  a  large  pinacoid  face,  b  (010)  was  devel- 
oped. The  plate  was  measured  in  a  monobromnaphthalene, 
whose  index  of  refraction  for  yellow,  Na,  was  found  to  be 
1.6588  at  23°  C.  The  values  obtained  were : 

For  yellow,  Na,  a  =  1.5043 
(3  =  1.5095 
y  =  1.5751 

By  means  of  the  three  indices  of  refraction  the  value  of 
Va.y  was  calculated  and  found  to  be  16°  24'. 

With  a  prism  of  56°  41;,  whose  faces  were  approximately 
parallel  to  110  and  110,  the  values  of  @  and  7  for  red,  Li ; 
yellow,  Na;  and  green,  Tl,  were  also  obtained. 

0  y 

Eed  1.5056  1.5710 

Yellow  1.5084  1.5747 

Green  1.5115  1.5789 

The  value  of  /3  for  yellow  is  probably  not  as  accurate  as 
that  obtained  by  means  of  total  reflection. 

The  divergence  of  the  optical  axes,  2E,  was  measured  on  a 
plate  parallel  to  010.  The  values  that  were  obtained  are  as 

follows : 

*  Ann.  d.  Phys.  u.  Chem.,  xx,  p.  592,  1883. 


BORAX  LAKE,  CALIFORNIA.  269 

Red,  Li.  Yellow,  Na.  Green,  Tl. 

2  E  at  25°C  =  47°  45'  48°  14'  48°  22' 

Hence  2V     =  31°  li  31°  26'  31°  27' 


The  value  of  Vfl>y  is  15°  43'  and  agrees  favorably  with  the 
value  16°  24'  obtained  by  calculation  from  the  three  indices  of 
refraction. 

It  was  observed  that  the  angle  2  E  varied  somewhat,  and 
to  determine  to  what  extent  this  was  dependent  upon  the 
temperature  the  following  measurements  were  made: 

Temperature        20°       30°        40°      50°        60°       70°       90°  C. 
2Ey          =  48°16'  48°10'  48°4'  47°55'  47°50'  47°45'  47°38' 

Chemical  composition.  —  Suitable  material  for  analysis  was 
readily  obtained  and  the  results  are  as  follows  : 


FTd' 


Ratio- 


C02  36.23  35.91  36.07      0.819                   2.00 

CaO  23.28  23.48  23.38      0.417                    1.02 

Na20  25.69  25.71  25.70       0.414  )041fi       -,  09 

K20  0.17  0.13  0.15      0.002) 

H20  14.74  14.73  14.73      0.818                    2.00 

A1208,  etc.  .  .  .  0.13  0.13 

Si02  0.36  0.22  0.29 

100.45 

The  ratio  for  CO2  :  CaO  :  Na2O  :  H2O  is  very  close  to 
2:1:1:2,  which  gives  the  formula  CaCO3  .  Na2CO3  .  2H2O. 
The  theoretical  composition  is  given  below,  together  with  the 
analysis,  after  deducting  impurities,  substituting  for  K2O  its 
equivalent  of  Na2O,  and  recalculating  to  100  per  cent. 

Wrmnri  Calculated  for 

md-         CaCOs  .  Na2C03  .  2H20. 

C02  .....  36.08  36.36 

CaO  .....  23.39  23.14 

Na2O  ....  25.80  25.62 

H20  .....  14.73  14.88 

100.00  100.00 


270  MINERALS   FROM 

The  chemical  composition  of  this  mineral  differs  from 
gay-lussite,  CaCO3 .  Na2CO3 .  5H2O,  in  having  only  two  instead 
of  five  molecules  of  water  of  crystallization.  Experiments 
that  were  made  to  determine  at  what  temperature  the  water  is 
driven  off  from  the  air-dry  powder  are  as  follows : 

Loss. 

Six  hours  at  100°  .  .  .  Nothing 
Ten  hours  at  150°  .  .  13.85 
Three  hours  at  200°  .  0.37 
Six  hours  at  250°  .  .  .  0.36 
Below  faint  redness  .  .  0.16 
Total 14.74 

As  practically  all  of  the  water  is  expelled  below  150°,  it 
must  be  regarded  as  water  of  crystallization. 

In  Analysis  I  the  water  was  weighed  directly  by  the  method 
described  by  Penfield,*  and  in  II  it  was  determined  by  loss  on 
gentle  ignition. 

Pyrognostics.  -  -  The  mineral  decrepitates  when  heated 
before  the  blowpipe,  and  fuses  about  2-2.5,  coloring  the 
flame  intensely  yellow.  It  reacts  alkaline  after  heating.  In 
the  closed  tube  it  decrepitates  and  gives  off  water  at  a  low 
temperature.  It  is  soluble  in  cold  dilute  hydrochloric  and 
nitric  acids  with  effervescence. 

Name.  —  The  author  takes  pleasure  in  naming  this  mineral 
pirssonite,  in  honor  of  his  friend  and  associate,  Professor  L.  V. 
Pirsson,  of  the  Sheffield  Scientific  School. 

HANKSITE. 

This  mineral  was  first  identified  in  1885  by  Mr.  W.  E. 
Hidden,!  who  observed  some  crystals  with  hexagonal  habit 
marked  thenardite,  in  the  mineral  exhibit  from  California,  at 
the  World's  Industrial  and  Cotton  Centennial  Exposition, 
held  in  New  Orleans.  Upon  examination  these  crystals 
proved  to  be  a  new  mineral,  to  which  the  name,  hank&ite,  was 

*  Amer.  Jour.  Sci.,  1894,  vol.  48,  p.  31. 
t  Amer.  Jour.  Sci.,  1885,  vol.  30,  p.  33. 


m 


BORAX  LAKE,  CALIFORNIA.  271 

given,  in  honor  of  Mr.  H.  G.  Hanks,  formerly  State  Mineral- 
ogist of  California. 

The  mineral  occurs  at  Borax  Lake  in  many  places.    Accord- 
ing to  information  received  from  Mr.  Northup,  short  crystals 
with  prominent  basal  planes  are  found  near  the  surface,  either 
attached  to  the  under  side  of  the  crust,  already  referred  to  on 
page  262  of  this  article,  or  in  the  mud  directly  beneath  this. 
The  habit  of  these  crystals  is  illustrated   by  figures   in   the 
articles  by  Hidden   and  Hanks.*     Beneath   the 
crust,  for  a  distance  of  about  50  feet,  hanksite 
crystals  are  rare,  but  at  this  depth  a  stratum  of 
mud  was  encountered,  containing  a  few  crystals 
with  a  habit  somewhat  resembling  quartz,  shown 
in  Figure  7.     The  crystals  were  etched  to  such 
an  extent  that  they  could  not  be  measured  with 
the  reflection  goniometer,  but  by  means  of  the      FIGURE  7 
contact  goniometer  the  forms  were  identified  as 
the  prism  m  (1010)  and  the  unit  pyramid  o  (1011). 

Optical  properties.  —  As  the  indices  of  refraction  of  hanksite 
had  not  been  determined,  a  basal  section  was  prepared  from  a 
tabular  crystal,  and  by  means  of  total  reflection  the  following 
values  were  obtained: 

For  yellow,  Na,  to  =  1.4807  €  =  1.4614. 

The  section  showed  a  normal  uniaxial  interference  figure 
and  a  strong  negative  double  refraction. 

Chemical  composition.  —  Our  knowledge  concerning  the 
chemical  composition  of  hanksite  is  confined  to  two  analyses. 
One  by  Mackintosh,  quoted  by  Hidden, f  from  which  the 
formula,  4Na2SO4  .  Na2CO3  .  £NaCl  was  derived.  Sodium 
chloride,  however,  was  regarded  as  non-essential  and  4Na2SO4  . 
Na2CO8  was  suggested  as  the  probable  formula.  It  should 
be  pointed  out,  however,  that  a  mistake  in  the  calculation  of 
the  analysis  was  made,  for  while  the  ratio  of  Na2SO4 :  Na2CO3 : 
NaCl  is  given  as  3.95  :  1  :  0.46  or  4  :  1  :  0.5,  it  should  have 

*  Amer.  Jour.  Sci.,  1889,  vol.  37,  p.  66. 
t  Amer.  Jour.  Sci.,  1885,  vol.  30,  p.  134. 


272  MINERALS  FROM 

been  4.6  :  1  :  0.53.  The  analysis  is  also  incomplete  since  the 
bases  are  calculated  wholly  as  soda. 

An  analysis  has  also  been  made  by  Penfield  *  on  material 
from  a  large  crystal  presented  to  the  Brush  collection  by  the 
late  Prof.  J.  S.  Newberry.  It  was  quite  impure,  apparently 
owing  to  included  clay,  the  analysis  giving  4.41  per  cent  of 
insoluble  material  and  1.32  per  cent  loss  on  ignition.  In 
addition  to  sodium,  2.33  per  cent  of  potassium  was  deter- 
mined, which  is  just  sufficient  to  unite  with  the  2.13  per  cent 
of  chlorine  to  form  potassium  chloride.  An  examination  of  a 
section  of  this  crystal  by  Prof.  E.  S.  Dana  f  showed  numerous 
rectangular  inclusions,  supposed  to  be  either  sodium  or  potas- 
sium chloride.  The  material  was  regarded  as  too  impure  to 
warrant  the  establishment  of  a  complicated  formula,  and  the 
results  of  the  analysis,  after  deducting  the  insoluble  material, 
loss  on  ignition,  and  KC1,  approximated  to  the  formula 
4Na2SO4  .  Na2CO3,  suggested  by  Mackintosh. 

In  making  the  optical  examination  of  the  hanksite  it  was 
observed  by  the  present  writer  that  although  the  sections, 
when  examined  with  the  microscope,  showed  trifling  im- 
purities, nothing  of  an  isometric  character  could  be  detected. 
Moreover,  on  testing  numerous  crystals  for  chlorine,  it  was 
found  to  be  invariably  present,  and  since  the  results  of  Pen- 
field  and  Mackintosh  have  shown  that  the  mineral  contains  an 
amount  of  chlorine  corresponding  to  over  4  per  cent  of  sodium 
or  potassium  chloride,  it  is  not  possible  that  either  of  these 
latter  compounds  could  be  present  to  such  an  extent,  as  an 
impurity,  without  being  detected  with  the  microscope.  It  was 
suggested,  therefore,  by  Prof.  Penfield,  that  new  analyses,  made 
on  the  exceptionally  pure  material  now  at  hand,  might  indicate 
that  chlorine  is  an  essential  constituent  of  the  mineral. 

Some  flat  tabular  crystals  were  therefore  selected,  and  in 
order  to  free  them  as  far  as  possible  from  any  impurities  they 
might  contain,  they  were  crushed  and  sifted  to  a  uniform 
grain  and  separated  by  means  of  methylen  iodide.  Most  of 
the  material  varied  in  specific  gravity  between  the  narrow 
*  Amer.  Jour.  Sci.,  1885,  vol.  30,  p.  137.  t  Loc.  cit. 


BORAX  LAKE,   CALIFORNIA.  273 

limits  2.567  and  2.553,  and  this  alone  was  used  for  the 
analysis. 

The  prismatic  crystals,  derived  from  the  stratum  of  mud 
fifty  feet  below  the  surface,  having  the  habit  shown  in  Figure 
7,  appeared  even  purer  than  those  mentioned  above,  and,  for- 
tunately, enough  of  these  had  been  supplied  by  Mr.  Northup 
for  an  analysis.  The  specific  gravity  was  found  to  be  2.545. 

The  results  of  the  analyses  of  the  two  samples  are  as 
follows : 

Tabular  Crystals.^        Averftge          Ratio  ^ismatic  Crystals. 

S03  45.89  .  .  .  45.98  45.93  0.574  9.00  45.78  0.572  9.00 

C02  ...  5.65  .  .  .  5.65  0.128  2.01  5.63  0.128  2.01 

Na20  43.27  .  .  .  43.43  43.35  0.699  10.95  43.61  0.703  11.07 

Cl  ...  2.21  ...  2.21  0.062  0.97  2.28  0.064  1.01 

K  2.40  ...  2.55  2.48  0.063  0.98  2.39  0.061  0.96 

Insol.  0.22  .  .  .  0.16  0.19  0.12 

The  analyses  are  almost  identical,  indicating  that  chlorine 
and  potassium  are  not  accidental  constituents.  The  ratios  of 
SO8 :  CO2  :  Na2O  :  Cl :  K  are  very  close  to  9  :  2  :  11  :  1  :  1 
corresponding  to  the  formula  9Na2SO4 .  2Na2CO3  .  KC1. 

Of  the  previous  analyses,  that  of  Mackintosh  yields  the 
ratio  of  SO3  :  CO2  :  Cl  =  9  :  1.93  :  1.04,  fully  supporting  the 
above  formula,  but  no  further  comparison  can  be  made,  as  the 
bases  were  calculated  wholly  as  soda.  The  analysis  of  Pen- 
field  gives  the  ratio  SO3  :  C02  :  Na2O  :  Cl  :  K  =  9  :  2.03  : 
10.89  :  0.99  :  0.99,  which  is  fully  in  accordance  with  the  above 
formula. 

Further,  in  order  to  show  the  close  agreement  between  the 
analytical  results  and  the  theoretical  composition,  the  analyses 
with  the  exception  of  that  of  Mackintosh  are  given  below, 
after  deducting  impurities  and  recalculating  to  100  per  cent. 

Tabular  Crystals.         Prismatic  Crystals.  Penfield's.  Theory. 

S03           46.11  45.92  46.21  46.02 

C02            5.66  5.65  5.74  5.62 

Na20        43.53  43.74  43.32  43.59 

Cl               2.215  2.29  2.26  2.26 

K               2.485  2.40  2.47  2.49 

100.000  lOOOO  100.00  100.00 

18 


274  MINERALS  FROM  BORAX  LAKE,   CAL. 

With  the  close  agreement  of  these  three  complete  analyses, 
together  with  the  partial  one  of  Mackintosh,  made  on  entirely 
different  samples,  on  crystals  collected  at  different  times  and 
from  different  parts  of  the  deposit,  there  can  be  no  doubt  that 
both  potassium  and  chlorine  are  essential  constituents  of  the 
compound  and  the  somewhat  complicated  formula,  9Na2SO4  . 
SNa^COg .  KC1  is  the  correct  one.  It  is  scarcely  possible  that 
potassium  and  sodium  are  isomorphous  in  this  mineral,  for 
potassium  seems  always  to  be  present  in  quantity  just  sufficient 
to  form  KC1  with  the  chlorine.  The  compound  furnishes  a 
very  interesting  example  of  the  exceptionally  rare  occurrence 
of  three  acid  radicals  in  a  mineral. 

In  conclusion,  the  author  wishes  to  express  his  indebtedness 
to  Professor  Penfield  for  his  valuable  advice  and  assistance, 
and  also  for  his  very  kind  interest  in  the  work,  throughout 
the  entire  investigation. 


ON  WELLSITE,  A  NEW  MINERAL. 

BY  J.  H.  PRATT  AND  H.   W.  FOOTE. 
(From  Amer.  Jour.  Sci.,  1897,  vol.  3,  443-448.) 

THE  mineral  to  be  described  in  this  article  occurs  at  the 
Buck  Creek  (Cullakanee)  corundum  mine  in  Clay  Co.,  North 
Carolina,  and  was  collected  by  Professor  S.  L.  Penfield  and  one 
of  the  present  writers  (Pratt)  during  the  summer  of  1892  while 
engaged  in  work  on  the  North  Carolina  Geological  Survey. 

The  corundum  vein  in  which  the  mineral  is  found  is  com- 
posed chiefly  of  albite,  feldspar,  and  hornblende,  and  penetrates 
a  peridotite  rock,  dunite,  near  its  contact  with  the  gneiss.  The 
peridotite  outcrop  is  one  of  the  largest  in  the  State  and  has 
been  thoroughly  prospected  for  corundum.  At  only  one  of 
the  veins  opened  was  the  new  mineral  found,  although  a  care- 
ful search  was  made  for  it  at  all  the  openings,  especially  those 
affording  feldspar.  No  mining  has  been  done  at  the  locality 
since  1891,  but  if  work  is  resumed  and  the  veins  uncovered, 
more  of  the  material  will  undoubtedly  be  found. 

The  mineral  is  found  in  isolated  crystals  mostly  attached  to 
the  feldspar  but  also  to  hornblende  and  corundum,  and  is  inti- 
mately associated  with  chabazite  which  occurs  in  small  trans- 
parent rhombohedrons. 

The  largest  crystals  that  were  observed  were  not  over  1  mm. 
in  diameter  and  2  mm.  in  length. 

Crystalline  form.  —  The  crystals  belong  to  the  monoclinic 
system  and  they  are  twinned  similarly  to  those  of  harmotome 
and  phillipsite.  The  common  habit  is  shown  in  Figure  1, 
which  represents  a  combination  of  twinning  about  c  (001)  and 
e  (Oil).  The  crystals  are  practically  square  prisms,  termi- 
nated by  pyramidal  faces,  thus  imitating  closely  a  simple  com- 
bination of  a  prism  of  one  order  and  a  pyramid  of  the  other  in 


276 


ON  WELLSITE, 


the  tetragonal  system.  The  apparent  prismatic  faces  are 
formed  for  the  most  part  by  the  pinacoid  faces,  ft,  but  the  crys- 
tals interpenetrate  each  other  somewhat  irregularly,  so  that  por- 
tions of  the  base  c  (001)  coincide  with  J,  Figure  1.  The  lines 
of  twinning  on  the  pinacoid  faces  between  b  and  b  twinned  are 
generally  regular,  while  those  between  b  and  c  and  also  those 
which  cross  the  prism  faces  m  (110)  (the  apparent  pyramid) 
are  generally  quite  irregular.  The  "b  faces  do  not  show  the 
striations  parallel  to  the  edges  b  and  m,  which,  meeting  along 
the  twinning  lines,  often  reveal  the  complex  nature  of  such 
crystals,  nor  were  any  reentrant  angles  observed  parallel  to  the 
edges  of  the  apparent  prism  as  are  common  on  phillipsite  and 
harmotome. 

Figure  2  represents  another  habit  of  the  crystals  where  m 
(110)  is  wanting  and  a  (100)  is  in  combination  with  b  (010). 
The  method  of  twinning  is  similar  to  that  already  described, 
but  the  crystals  being  terminated  by  a  (100)  instead  of  m 
(110)  show  prominent  reentrant  angles  at  their  ends.  These 
crystals  are  very  similar  to  those  of  harmotome  from  Bowling 
near  Dumbarton,  on  the  Clyde,  described  by  Lacroix.* 


FIGURE  1. 

The  only  forms  that  were  observed  were  a  (100),  b  (010), 
c  (001),  and  m  (110),  with  e  (Oil)  only  as  twinning  plane. 

The  faces  of  the  crystals  are  somewhat  rounded  and  vicinal 
so  that  reflections  were  not  very  perfect.  The  angle  of  the 
apparent  prism  b  A  b  twinned  is  approximately  90°.  Also 
the  angle  m  A  m  over  the  twinning  plane  (Oil)  could  be  mea- 

*  Bull.  Soc.  Min.  de  France,  No.  4,  p.  94, 1885. 


A  NEW  MINERAL. 


277 


sured  only  approximately,  varying  from  0°  49'  to  1°  25'.  The 
approximate  angles  are  given  below,  and  from  those  marked 
with  asterisks  the  following  axial  ratio  was  calculated : 


a  :  b  :  c  =  0.768  :  1  :  1.245 ;  £  =  53°  27'  =  001  A  100 


Measured. 


Calculated. 


b  A  b,  010  A  010 
a  A  a,  100  A  100 
b  A  m,  010  A  110 
c  A  a,  001  A  100 
c  A  m,  001  A  110 


*90°  (over  twinning  plane) 
*73°  6'  (over  twinning  plane) 
*58°  19' 

53°  27'  =  (3 

60°  00',  59°  45',  59°  57'  59°  33' 


Physical  properties.  —  The  crystals  are  brittle  and  show  no 
apparent  cleavage.  The  luster  is  vitreous.  Many  of  the 
crystals  are  colorless  and  transparent,  while  others  are  white. 
The  hardness  is  between  4  and  4.5.  The  specific  gravity 
taken  on  a  number  of  separate  crystals,  by  means  of  the 
heavy  solution,  varied  between  2.278  and  2.366.  This  vari- 
ation was  probably  due  to  the  difference  in  the  ratio  of  the 
barium  to  the  calcium  in  the  different  crystals. 

A  section  parallel  to  the  pinacoid 
b  (010),  the  apparent  prism,  revealed 
in  polarized  light  the  structure 
shown  in  Figure  3.  The  parts  I 
and  I  extinguish  simultaneously,  as 
also  II  and  II ;  while  portions  III, 
which  are  parallel  to  the  basal  plane, 
show  parallel  extinction.  The  sec- 
tion showed  something  of  a  zonal 
structure,  so  that  the  extinction 
could  be  measured  only  approxi- 
mately. Using  the  Bertrand  ocular, 
this  was  found  to  be  33°  from  one 
pinacoid  on  to  the  other  over  the 
twinning  plane.  The  axis  a  makes 
an  angle  of  52°  with  the  vertical  axis  c  in  the  obtuse  angle  fi. 

The  double  refraction  is  positive   and  weak.     The   acute 


FIGURE  3. 


278  ON   WELLSITE, 

bisectrix  t  is  at  right  angles  to  the  pinacoid  010,  and  the 
divergence  of  the  optical  axes  is  large.  2E  probably  varies 
from  120°  to  130°,  but  this  could  not  be  measured  directly. 

Chemical  analysis.  —  The  mineral  was  purified  for  analysis 
by  means  of  the  heavy  solution  and  that  which  was  used 
varied  in  specific  gravity  from  2.278  to  2.360.  Water  was 
determined  by  loss  on  ignition  and  silica  and  alumina  by  the 
ordinary  methods  after  fusion  with  sodium  carbonate.  The 
filtrate  from  the  alumina  precipitation  was  evaporated  with 
aqua  regia  to  remove  the  large  excess  of  ammonium  salts  and 
a  small  amount  of  ammonium  chloride  was  again  added.  Cal- 
cium, barium  and  strontium  were  then  precipitated  together, 
with  a  considerable  excess  of  ammonia  and  ammonium  carbo- 
nate, and  magnesia  was  determined  in  the  filtrate.  The  mixed 
carbonates  were  dissolved  in  hydrochloric  acid,  evaporated  to 
dryness  and  taken  up  in  about  300  c.  c.  of  water.  The  method 
used  for  separating  barium  was  that  recommended  by  Fre- 
senius.*  To  the  hot  solution,  a  few  drops  of  acetic  acid  were 
added  and  10  c.  c.  of  a  10  per  cent  solution  of  ammonium 
chromate  containing  a  small  amount  of  dichromate.  After 
standing  until  the  solution  became  cold,  the  clear  liquid  was 
decanted  and  the  precipitate  of  barium  chromate  was  washed 
with  a  weak  chromate  solution  and  with  water.  The  precipi- 
tate was  dissolved  in  2  c.  c.  of  pure  dilute  nitric  acid,  which  was 
then  partly  neutralized  with  ammonia.  Ammonium  acetate 
was  added  and  10  c.  c.  of  chromate  solution  as  before,  and  after 
standing,  the  precipitate  was  filtered  on  a  Gooch  crucible  and 
weighed  as  BaCrO4.  The  filtrate  from  the  barium  precipita- 
tion was  concentrated  somewhat,  and  calcium  and  the  small 
quantity  of  strontium  precipitated  as  before.  They  were 
ignited  and  weighed  as  oxide.  Strontium  was  then  separated 
by  treatment  with  amyl  alcohol  and  determined  as  sulphate. 
The  alkalies  were  determined  by  a  Smith  fusion  in  the 
ordinary  way. 

The  results  of  the  analyses  are  as  follows : 

*  Zeitschr.  Anal.  Chem.  xxix,  426. 


A   NEW  MINERAL. 


279 


ii. 


Average. 


Ratio. 


SiO2 
A1208 
BaO 

43.62 
25.04 
5.00 

SrO 

1.12 

CaO 

5.76 

MgO 
K20 

0.61 

H20 


13.32 


3.40 
1.80 


44.11 

43.86 

0.731 

24.89 

24.96 

0.244 

5.15 

5.07 

0.033  ' 

1.18 

1.15 

0.011 

5.84 

5.80 

0.104 

0.62 

0.62 

0.015 

.  .  . 

3.40 

0.036 

.  .  . 

1.80 

0.029 

13.39 

13.35 

0.742 

100.01 


3.00 
1.00 


>  0.228      0.93 


3.04 


The  ratio  of  SiO2  :  A12O3  :  RO  :  H2O  is  very  close  to  3  :  1  : 
1 :  3,  which  gives  the  formula  R"Al2Si8Oi0  .  3H2O.  The  ratio 
of  BaO  :  CaO  :  K2O  +  Na2O  in  the  above  analyses  is  nearly 
1:3:2  and  the  theoretical  composition  calculated  for  this 
ratio  is  given  below  together  with  the  analysis  after  substi- 
tuting for  Na2O  its  equivalent  of  K2O,  and  for  MgO  and  SrO 
their  equivalents,  respectively,  of  CaO  and  BaO,  and  then  re- 
calculating to  100  per  cent. 


Si02    .  . 

.  .  .  43.12 

ALO, 

.  .  .  24.54 

BaO 

6.65 

CaO        .  . 

.  .  .     6.59 

K20 

.      .     5.98 

H2O 

.  .  13.12 

Theory  for  R"Al2Si8O10 .  3H2O 
where  R  is  }Ba,  $Ca,  ?K. 

42.87 

24.27 
6.62 

7.27 

6.10 

12.87 


100.00 


100.00 


Experiments  were  made  to  determine  at  what  temperatures 
the  water  was  driven  off,  and  the  results  are  given  in  the  fol- 
lowing table,  the  mineral  being  heated  in  each  case  until  the 
weight  became  constant.  The  last  trace  of  water  could  only 
be  driven  off  by  heating  the  mineral  over  the  blast  lamp. 


280  ON  WELLSITE, 

Loss. 

At  100°  C  .........  nothing. 

125         ........  1.93) 

175         ........  1.48  U.33 

200         ........  0.92  ) 

260         ........  2-45 

295         ........  1.24 

Ked  heat  .......  4.96  ) 

Over  blast  lamp  .....  0.33  j  D 

Total  .........  13.31 


As"  is  seen  from  the  above,  about  one-third  of  the  water,  or 
one  molecule,  is  given  off  between  100°  and  200°,  another 
third  approximately  between  200°  and  300°,  while  the  remain- 
der is  expelled  only  at  an  intense  heat.  This  would  indicate 
that  the  water  exists  in  three  different  conditions  in  the  mole- 
cule. If  only  that  which  is  expelled  below  200°  be  regarded 
as  water  of  crystallization,  the  composition  would  be  H4R"A12 
Si3012  +  H20. 

That  the  new  mineral  would  be  closely  related  to  the  phil- 
lipsite  group  of  the  zeolites,  was  expected  from  the  first,  on 
account  of  its  crystalline  form,  and  this  relation  is  very  satis- 
factorily brought  out  by  a  comparison  of  the  crystallographic 
properties  and  chemical  composition. 

They  all  have  very  nearly  the  same  axial  ratios  : 


Wellsite  0.768      :  1  :  1.245 ;       £  =  53°  27' 

Phillipsite  0.70949  :  1  :  1.2563  ;     /?  =  55°  37' 

Harmotome  0.70315  :  1  :  1.2310  ;     /?  =  55°  10' 

Stilbite  0.76227  :  1  :  1.19401 ;  j3  =  50°  49f 

In  their  habit  and  method  of  twinning,  they  are  also  very 
similar,  all  the  crystals  being  uniformly  penetration  twins. 
This  is  especially  noticeable  between  the  new  mineral  and 
phillipsite  and  harmotome  which  are  common  as  double  twins 
with  c  (001)  and  e  (Oil)  as  twinning  planes. 

The  place  of  the  mineral  in  the  phillipsite  group  is  clearly 


A   NEW  MINERAL.  281 

shown  by  a  comparison  of  their  chemical  compositions.  Ar- 
ranged in  order  of  their  proportions  of  silica  and  water  to 
the  bases,  we  have  the  following  interesting  series,  in  which 
R  represents  the  bivalent  elements : 

Wellsite EAl2Si3O10 .  3H20 

Phillipsite     EAl2Si4012 .  4|H20 

Harmotome RAl2Si5014 .  5H20 

Stilbite RAl2Si6016 .  6H20 

The  ratio  of  RO  :  A12O3  is  constant,  1  :  1,  in  the  series, 
while  the  proportions  of  silica  and  water  have  a  constant  ratio, 
1:1,  between  themselves,  except  in  the  case  of  phillipsite. 
As  there  is,  however,  considerable  variation  in  the  analyses  of 
phillipsite,  it  is  not  improbable  that  the  ratio  of  SiO2  :  H2O, 
given  as  4  :  4J,  should  be,  in  some  cases  at  least,  4  :  4.  The 
minerals  then  form  a  gradual  series,  increasing  in  the  propor- 
tions of  SiO2  and  H2O  from  wellsite  to  stilbite.* 

Fresenius  f  has  shown  that  this  group  of  minerals  may  be 
regarded  as  a  series  in  which  the  ratio  of  RO  :  A12O3  is  con- 
stant, 1:1,  while  the  silica  and  water  vary  between  certain 
limits.  He  has  assumed  as  these  two  limits : 


*  The  following  analysis  of  a  very  pure  phillipsite  from  Bass  Strait, 
South  Australia,  made  by  Mr.  G.  H.  Edwards  of  the  Sheffield  Laboratory 
and  here  published  for  the  first  time,  confirms  the  assumption  made  by  Pratt 
and  Foote  that  the  ratio  of  SiO2  :  H20  in  phillipsite  is  4  :  4  and  not  4  :  4£  : 

Specific  gravity  2.218        Ratio. 

4.00 

1.06 


0.196  0.98 


4.14 
100.64 

The  ratio  SiO2 :  A1203 :  RO  :  H20  approximates  closely  to  4  :  1  :  1  :  4,  agreeing 
with  the  formula  RAl2Si4O12  .  4H2O,  R  =  K2,  Na2,  Ca,  Ba,  and  Sr.  — EDITOR. 
t  Zeitschr.  Kryst.,  vol.  3,  p.  42,  1878. 


Si09   .  . 

...    47  94 

0799 

AloO,     , 

21  72 

0213 

.  .  .      044 

BaO   

SrO    .      ... 

'  '  '  |    0.77 

0.007 

CaO    .  .     .  . 

.     .      225 

0040 

Na2O  

.  .  .      2.73 

0044 

K20 

9  87 

0  105 

H2O    .... 

1492 

0829 

282  ON  WELLSITE. 

RAl2Si6016   +  6H20  and 
K2Al4Si4016  +  6H2O. 

The  first  would  be  a  hydrated  calcium  albite  and  the  last 
a  hydrated  anorthite.  From  a  comparison  of  the  wellsite- 
stilbite  series,  it  seems  more  probable  that  the  anorthite  end 
would  be  RAl2Si2O8  +  2H2O,  or  doubling  this  for  better  com- 
parison with  the  formula  of  Fresenius,  R2Al4Si4O16  +  4H2O. 

It  is  not  unreasonable  to  expect  that  the  first  or  anorthite 
member  of  this  series  may  be  found  in  nature  and  the  com- 
pleted series  would  then  be  : 

Anorthite  limit  .  .  .  KAl2Si208   +  2H20  (not  yet  identified) 

Wellsite RAl2Si3010  +  3H20 

Phillipsite RAl2Si4012  +  4H2O 

Harmotome RAl2Si5O14  +  5H20 

Stilbite RAl2Si6016  +  6H20 

It  is  also  interesting  to  note  that  the  formula  of  the  new 
mineral  wellsite  is  the  same  as  that  assigned  to  edingtonite, 
but  the  latter  is  essentially  a  barium  mineral,  and,  being  tetra- 
gonal, shows  no  crystallographic  relations  to  wellsite. 

Pyrognostics.  —  When  heated  before  the  blowpipe,  well- 
site  exfoliates  slightly  and  fuses  at  2.5-3  to  a  white  bead, 
coloring  the  flame  slightly  yellow.  In  the  closed  tube,  water 
is  given  off  at  a  low  temperature.  It  is  very  readily  decom- 
posed by  hot  hydrochloric  acid  with  the  separation  of  silica, 
but  without  gelatinization.  When  the  water  in  the  mineral 
is  driven  off  below  265°  C.,  it  is  nearly  all  regained  on  expos- 
ing the  mineral  to  the  air.  If  the  water,  however,  is  driven 
off  at  a  red  heat,  none  is  regained  by  the  mineral. 

Name.  —  It  is  with  pleasure  that  the  authors  name  this 
mineral  wellsite  in  honor  of  their  friend  Professor  H.  L.  Wells 
of  the  Sheffield  Scientific  School. 

In  conclusion,  the  authors  wish  to  express  their  thanks  to 
Professor  Penfield  for  advice  and  suggestions  and  the  kind 
interest  he  has  shown  during  the  investigation. 


ON  BIXBYITE,  A  NEW  MINERAL. 

BY  S.  L.  PENFIELD  AND  H.  W.  FOOTE. 
(From  Amer.  Jour.  Sci.,  1897,  vol.  4,  pp.  105-107.) 

THE  mineral  to  be  described  in  the  present  article  was  sent 
to  us  for  identification  by  Mr.  Maynard  Bixby,  of  Salt  Lake 
City,  Utah.  Concerning  its  occurrence  we  are  informed  that 
the  mineral  is  found  very  sparingly  in  one  or  two  small  areas  on 
the  edge  of  the  desert  about  thirty-five  miles  southwest  of 
Simpson,  Utah.  The  crystals  are  implanted  upon  topaz  and 
decomposed  garnet  and  rhyolite,  and  have  evidently  been 
formed  by  fumarole  action. 

The  mineral  crystallizes  in  the  isometric  system,  usually  in 
cubes,  some  of  which  measure  over  5  mm.  on  an  edge.  These 
are  occasionally  modified  by  the  trapezohedron  (211)  and  on 
one  small  specimen  the  cubes  and  trapezohedrons  are  developed 
with  almost  ideal  symmetry  as  shown  in 
the  accompanying  figure.  When  meas- 
ured on  the  goniometer  the  crystals  gave 
fairly  good  reflections  of  the  signal,  and 
211  A  112  was  found  to  be  33°40':  cal- 
culated 33°  331'.  The  mineral  breaks 
with  an  irregular  fracture,  and  on  one 
or  two  specimens  traces  of  octahedral 
cleavage  were  observed.  The  color  is 

brilliant-black  with  metallic  luster,  and  the  streak  is  black. 
The  hardness  is  6  to  6.5.  The  specific  gravity  of  the  material 
used  for  the  quantitative  analysis  was  taken  on  a  chemical 
balance  and  found  to  be  4.945.  The  mineral  fuses  before  the 
blowpipe  at  about  4  and  becomes  magnetic.  When  very  finely 
powdered,  it  dissolves  with  some  difficulty  in  hydrochloric  acid 
with  evolution  of  chlorine. 


284  ON  BIXBYITE, 

Method  of  Analysis.  —  The  material  for  analysis  was  sepa- 
rated in  a  nearly  pure  condition  by  the  thallium-silver  nitrate 
mixture.  The  mineral  was  treated  with  strong  hydrochloric 
acid  in  a  flask  connected  with  a  condenser,  and  the  chlorine 
liberated  was  distilled  over  into  a  solution  of  potassium  iodide. 
Free  iodine  was  then  determined  volumetrically  with  standard 
thiosulphate  and  iodine  solutions,  from  which  the  amount  of 
available  oxygen  was  calculated.  After  filtering  off  a  small 
amount  of  insoluble  material,  iron,  aluminium  and  titanium 
were  separated  from  manganese  and  magnesium  by  the  basic 
acetate  method.  The  three  oxides  were  weighed  together,  iron 
was  then  determined  by  titration  with  permanganate  solution 
and  titanium  was  twice  precipitated  by  boiling  the  nearly  neu- 
tral dilute  sulphate  solution  for  two  hours  in  the  presence  of 
sulphur  dioxide.  It  was  weighed  as  TiO2.  From  the  filtrate 
from  the  basic  acetate  precipitation,  manganese  was  precipi- 
tated with  excess  of  bromine  water.  The  precipitate,  after 
filtering,  was  dissolved  in  a  solution  of  sulphur  dioxide,  pre- 
cipitated as  phosphate  and  weighed.  Magnesium  was  precipi- 
tated from  the  first  manganese  filtrate  as  phosphate. 

Following  are  the  results  of  the  analyses : 


i. 

IL 

Average. 

Ratio. 

Si02 

1.24 

1.19 

1.21 

•   .   * 

A1203 

2.57 

2.48 

2.53 

.    .    . 

Fe203 

47.81 

48.15 

47.98 

0.300 

Ti02 

1.62 

1.78 

1.70 

0.022 

MnO 

42.08 

42.02 

42.05 

0.592 

MgO 

0.12 

0.09 

0.10 

0.002 

Available  0 

4.37 

4.39 

4.38 

0.274 

99.81 

100.10 

99.95 

The  silica  and  alumina  are  regarded  as  impurities,  as  only  a 
trace  of  them  went  into  solution  when  the  mineral  was  treated 
with  hydrochloric  acid.  In  preparing  the  mineral  for  analysis, 
a  variation  in  specific  gravity  was  observed,  owing  to  the  fact 
that  some  of  the  dark  particles  were  buoyed  up  by  impurities, 
but  in  order  to  obtain  sufficient  material  for  analysis,  it  was 


A   NEW  MINERAL.  285 

necessary  to  include  some  of  the  lighter  portion.  It  is  prob- 
able from  the  results  of  the  analysis  that  some  topaz  was 
present,  for  the  ratio  of  silica  to  alumina  is  about  1 :  1  and 
topaz  is  intimately  associated  with  the  bixbyite. 

Leaving  silica  and  alumina  out  of  account,  two  formulas  are 
possible.  Considering  the  titanium  as  Ti2O8,  the  oxygen 
derived  from  the  TiO2,  0.16  per  cent,  plus  the  available  oxygen, 
4.38  (total  4.54  per  cent)  is  about  sufficient  to  convert  the  MnO 
into  Mn2O3,  the  amount  required  for  42.05  per  cent  MnO 
being  4.74.  The  composition  therefore  may  be  expressed  as 
RaO3,  where  R  =  Fe,  Mn,  and  a  little  Ti.  The  proportion  of 
Fe  to  Mnis  1 :  0.99  or  almost  1 :  1,  so  that  disregarding  Ti2O3, 
the  composition  is  FeMnO3.  If  the  mineral  is  an  isomorphous 
mixture  of  Fe2O3,  Mn2O3  and  Ti2O3  we  should  expect  it  to  be 
rhombohedral  and  to  belong  to  the  hematite  and  corundum 
group,  and  also  it  is  not  probable  that  the  Fe  and  Mn  would 
be  present  in  the  proportion  1:1. 

As  the  mineral  is  isometric,  it  seems  more  reasonable  to 
regard  it  as  a  compound  having  essentially  the  composition 
FeO .  MnO2,  and  related  to  the  isometric  mineral  perofskite, 
CaO .  TiO2.  On  this  basis,  the  results  of  the  analysis  may  be 
put  in  the  following  shape : 

Ratio. 

FeO 43.17  0.600  ) 

MgO 0.10  0.002  ) 

MnO 42.05  0.592 

Ti02 1.71  0.021 

Avail.  O  and  0  from  Fe203     9.18  0.574 

Si02 1.21 

A1203 2.53 

99.95 

The  ratio  of  Fe  +  Mg  :  Ti  +  Mn  is  0.602  :  0.613  or  nearly 
1:1,  while  the  oxygen  is  almost  sufficient  to  convert  the  MnO 
into  MnO2  as  indicated  by  the  ratio  MnO  :  O  =  0.592 :  0.574.  As 
oxygen  was  determined  perhaps  as  accurately  as  any  other  con- 
stituent, it  seems  possible  that  a  small  amount  of  manganese 
may  be  present  as  protoxide,  replacing  FeO.  If  enough  man- 


286  ON  BIXBYITE. 

ganese  be  taken  as  protoxide  to  make  the  ratio  of  RO  to  RO2 
exactly  1  :  1,  the  results  become : 

Ratio. 

FeO     43.17  0.600) 

MgO 0.10  0.002  V-0.608 

MnO 0.40  0.006) 

TiOa    1.71  °-02 

MnO 41.65  0.587 

0 9.18 

Si02     1.21 

A1208 2.53 

99.95 

The  oxygen  necessary  to  convert  41.65  per  cent  of  MnO  to 
MnO2  is  9.38,  which  is  only  slightly  in  excess  of  that  actually 
found  in  the  analysis.  It  seems  therefore  probable  that  the 
mineral  is  essentially  FeMnO8  =  FeO  .  MnO2,  in  which  small 
quantities  of  MgO  and  MnO  are  isomorphous  with  FeO  and  a 
little  TiO2  with  MnO2.  The  mineral  is  therefore  to  be  regarded 
as  a  ferrous  salt  of  manganous  acid,  H2MnO8,  corresponding  to 
braunite  MnMnO3,  which  is  supposed  to  be  the  manganese  salt 
of  the  same  acid. 

We  take  pleasure  in  naming  this  mineral  after  Mr.  Bixby, 
who  has  generously  supplied  us  with  material  for  investiga- 
tion, and  has  gone  to  a  great  deal  of  trouble  and  pains  to 
secure  the  specimens. 


ON  THE  CHEMICAL  COMPOSITION  OF  HAMLIN- 
ITE  AND  ITS  OCCURRENCE  WITH  BERTRAN- 
DITE  AT  OXFORD  COUNTY,  MAINE. 

BY  S.  L.  PENFIELD. 
(From  Amer.  Jour.  Sci.,  1897,  vol.  4,  pp.  313-516.) 

IN  the  summer  of  1890,  Mr.  W.  E.  Hidden  and  the  author 
published  a  short  description  of  a  rhombohedral  phosphate 
occurring  with  the  rare  minerals  herderite  and  bertrandite  at 
Stoneham,  Maine.  Only  a  single  specimen,  showing  a  few 
minute  crystals,  was  ever  found  at  the  locality,  and  the  inves- 
tigation was  therefore  incomplete,  being  confined  to  determina- 
tions of  the  crystallization  and  physical  properties  and  the 
identification  of  phosphorus,  aluminium,  fluorine,  and  water, 
while  from  its  association  it  was  supposed  that  it  would  also 
contain  beryllium. 

The  mineral  was  named  hamlinite  in  honor  of  Augustus  C. 
Hamlin  of  Bangor,  Maine,  who  has  always  taken  a  keen  interest 
in  collecting  and  studying  the  minerals  of  his  State,  and  espe- 
cially the  beautiful  tourmalines  from  Mt.  Mica  and  vicinity. 
As  stated  in  the  original  article,  the  incomplete  description 
was  published  for  the  purpose  of  calling  attention  to  a  mineral 
which  would  probably  prove  to  be  interesting,  and  also  in 
hopes  that  others  would  be  led  to  look  for  the  mineral  and  find 
it.  This  hope  has  not  been  in  vain,  for  Mr.  Lazard  Cahn  of 
New  York  had  the  good  fortune  to  discover  among  a  suite  of 
minerals  from  Oxford  County,  Maine,  some  specimens  showing 
rhombohedral  crystals  of  a  mineral,  unknown  to  him,  which  he 
gave  to  the  author,  suggesting  that  they  might  prove  to  be  the 
rare  mineral  hamlinite.  It  is  hoped  that  additional  informa- 
tion may  be  obtained  concerning  the  exact  locality  at  which 
the  mineral  is  found,  so  that  a  supply  of  specimens  may 
become  available  for  distribution.  The  mineral  was  readily 


288         CHEMICAL   COMPOSITION  OF  HAMLINITE 

identified  as  hamlinite  by  its  rhombohedral  crystallization,  basal 
cleavage,  positive  double  refraction,  and  blowpipe  reactions. 

The  crystals  are  implanted  upon  feldspar  and  muscovite  and 
are  associated,  like  the  ones  from  Stoneham,  with  apatite,  her- 
derite  and  rarely  bertrandite.  The  crystals  present  two  promi- 
nent habits :  One  a  combination  of  the  rhombohedrons  r(1011) 
and  /(0221),  developed  as  shown  in  the  accompanying  figure. 
On  these  crystals  there  are  occasionally  small 
basal  planes  and  slight  horizontal  striations  on 
the  rhombohedral  faces  near  their  juncture 
with  the  base.  The  other  habit  is  essentially 
a  combination  of  the  hexagonal  prism  of  the 
first  order  (1010)  with  the  base,  but,  owing  to 
a  vicinal  development  and  rounding,  the  pris- 
matic faces  have  a  tendency  toward  a  steep 
rhombohedral  development,  and  the  basal 
planes  are  marked  by  triangular  prominences. 
The  crystals  attain  at  times  a  diameter  of  3  to  4  mm.,  but 
are  not  well  adapted  for  measurement  owing  to  the  vicinal 
character  of  the  faces.  The  following  measurements  can 
claim  to  be  only  approximations,  since  there  were  usually 
several  reflections  of  the  signal  of  the  goniometer  from  each 
face,  and  it  was  impossible  to  tell  upon  which  one  the  cross- 
hair of  the  telescope  should  be  placed.  The  calculated  angles 
are  those  derived  from  measurements  of  the  hamlinite  from 
Stoneham,  c  =  1.135,  but  the  crystals  from  that  locality 
showed  a  vicinal  development  of  their  faces,  and  the  values 
cannot,  therefore,  be  considered  as  very  exact. 

Measured.  Calculated. 

r  A  r,  10T1  A  T101  =    88°  41'  87°  2' 

/A/,  0221  A  2021  =  1.09°  11'  108°  2" 

r  A/,  10T1  A  0221  =    54°  44'  and  54°  47'         54°  1' 

It  was  found  to  be  practically  impossible  to  select  by  hand- 
picking  a  sufficient  quantity  of  the  pure  hamlinite  crystals  for 
an  analysis,  and,  therefore,  a  number  of  specimens  upon  which 
the  crystals  were  observed  were  pulverized,  and  the  hamlinite 


AND  ITS   OCCURRENCE  IN  MAINE.  289 

separated  from  the  other  minerals,  by  means  of  the  heavy 
liquids.  Apatite,  however,  could  not  be  thus  separated,  but, 
owing  to  the  fact  that  hamlinite  is  almost  insoluble  in  boiling 
dilute  hydrochloric  acid,  it  was  possible  by  treatment  with 
successive  portions  of  acid  until  the  solution  gave  no  test 
for  calcium,  to  remove  the  apatite  completely.  All  possible 
precautions  were  taken  to  make  the  separation  and  purification 
of  the  mineral  as  complete  as  possible,  and  the  mineral,  when 
examined  with  the  microscope,  showed  no  visible  impurity. 
The  specific  gravity  of  the  hamlinite  varied  considerably,  that 
portion  which  was  taken  for  the  chemical  analysis  being 
between  3.159  and  3.283,  while  some  of  the  mineral  was  still 
a  trifle  higher  and  some  a  little  lower. 

A  qualitative  analysis  indicated  the  presence  of  aluminium, 
strontium,  barium,  phosphorus,  fluorine,  and  water,  and  the  ab- 
sence of  calcium  and  beryllium.  In  the  quantitative  analyses 
the  strontium  and  barium  were  weighed  together  as  sulphates 
and  subsequently  separated  as  recommended  by  Fresenius,*  by 
a  double  precipitation  of  the  barium  as  chromate.  The  fluorine 
was  weighed  as  calcium  fluoride,  and  the  latter  was  tested  and 
found  to  be  pure  by  conversion  into  sulphate.  Water  was  deter- 
mined in  two  ways ;  first  by  fusing  with  dry  sodium  carbonate 
and  weighing  the  water  directly,  f  second  by  loss  on  ignition, 
using  a  weighed  quantity  of  lime  to  retain  the  fluorine.^  The 
air-dry  powder  lost  only  0.16  per  cent  by  heating  to  100°,  and 
the  water  was  not  expelled  until  the  mineral  was  heated  nearly 
to  redness,  thus  indicating  the  presence  of  hydroxyl. 
The  results  of  the  analysis  are  given  on  p.  290. 
The  ratio  of  P2O5 :  A12O3  :  (Sr  +  Ba)O  :  (OH  +  F)  is  very 
nearly  1  :  1.5  :  1  :  7,  which  gives  the  formula  Al3Sr(OH)7 
P2O7  or  better  [Al(OH)2]3[SrOH]P2O7,  where  strontium  is 
partially  replaced  by  barium,  and  hydroxyl  by  fluorine. 

By  the  method  of  preparing  the  mineral  for  analysis  traces 
of  adhering  feldspar  and  mica  could  not  be  wholly  avoided, 
and,  although  the  small  quantities  of  Fe2O3  and  alkalies  may 

*  Zeitschr.  fur  anal.  Chemie,  xxix,  p.  413,  1890. 

t  Amer.  Jour.  Sci.,  1894,  vol.  48,  p.  37.  J  Ibid.,  1896,  vol.  32,  p.  109 

19 


290 


CHEMICAL   COMPOSITION  OF  HAMLINITE. 


P206 

A1203 
Fe203 
SrO 
BaO 
H2O 
F 
Si02 
K20 
Na20 

Oxyger 

32.29 

18.33 
4.10 

32.30 
0.90 
18.53 
3.89 

28.9 

ii.9 

2 

3        12.0 

Average. 
28.92 
32.30 
0.90 
18.43 
4.00 
7        12.00  H- 
1.93 
0.96 
0.34 
0.40 

Ratio. 
0.204 
0.316 

0.178  ) 
0.026  } 
9  =  1.333  ) 
0.102  ] 

1.93 
0.96 

L  equival 

0.34 
0.40 

2nt  of  flue 

)rine 

100.18 

0.81 
99.37 

1.00 
1.55 

0.204        1.00 
1.435        7.03 


belong  partly  to  the  hamlinite  and  partly  to  impurities,  these 
have  been  neglected  in  making  the  calculations.  If  the 
alkalies  together  with  their  equivalent  of  A12O3  (1.06  per 
cent),  the  Fe2O3  and  the  SiO2,  in  all  3.62  per  cent,  are  deducted 
from  the  analysis  and  the  remainder  calculated  to  one  hundred 
per  cent,  the  results  are  as  given  below,  where  they  are 
compared  with  the  theoretical  composition,  where  Sr  :  Ba  == 
7  :  1  and  OH  :  F  =  13  :  1. 


PoO* 

Found. 

30  20 

Calculated. 

30.31 

AloOo 

.  3267 

32.65 

SrO    

19.25 

19.29 

BaO 

.      .  .     4.18 

4.08 

H90   . 

12.53 

12.48 

F  

.  .      .  .     2.01 

2.04 

0-F   . 

100.84 
0.84 

100.85 
0.85 

In  its  chemical  composition  hamlinite  holds  a  unique 
position  among  minerals,  as  strontium  and  barium  have 
never  before  been  observed  as  essential  constituents  of  a 
phosphate,  and  this  is  the  first  time  that  a  pyrophosphate  has 
been  recorded. 


ON    CLINOHEDRITE,    A    NEW     MINERAL    FROM 
FRANKLIN,   N.   J. 

BY  S.  L.  PENFIELD  AND  H.   W.  FOOTE. 
(From  Amer.  Jour.  Sci.,  1898,  vol.  5,  pp.  289-293.) 

THE  mineral  that  is  to  be  described  in  the  present  paper  was 
first  brought  to  our  notice  in  the  autumn  of  1896  by  Mr. 
Frank  L.  Nason  of  West  Haven,  Conn.,  who  sent  a  few  speci- 
mens of  it  to  the  Mineralogical  Laboratory  of  the  Sheffield 
Scientific  School  for  identification.  When  informed  that  the 
mineral  was  a  new  species  Mr.  Nason  visited  the  locality  for 
the  special  purpose  of  obtaining  more  material,  but  so  little 
was  found  that  it  seemed  best  to  postpone  the  investigation 
until  more  could  be  secured.  About  a  year  later  Mr.  E.  P. 
Hancock  of  Burlington,  N.  J.,  sent  some  Franklin  minerals  to 
our  laboratory  for  identification,  among  them  specimens  of  the 
new  mineral,  and  on  learning  the  nature  of  the  mineral  he 
took  a  keen  interest  in  having  it  investigated,  generously 
placing  at  our  disposal  for  that  purpose  the  few  specimens  he 
had  collected.  A  short  time  later  Mr.  W.  F.  Ferrier  of 
Ottawa,  Canada,  also  called  our  attention  to  an  exceptionally 
fine  specimen  of  the  mineral,  which  he  had  had  the  good 
fortune  to  find  at  the  locality. 

The  specimens  were  all  obtained  from  the  dump  of  one  of 
the  new  shafts  of  the  Trotter  mine,  and  are  supposed  to  have 
come  from  a  depth  of  about  one  thousand  feet.  The  mineral 
is  associated  with  transparent  prisms  of  green  willemite,  a 
massive  variety  of  brown  garnet,  phlogopite  mica,  small  yellow 
crystals  of  axinite,  dull  crystals  of  datolite,  and  a  reddish- 
brown  mineral,  occurring  in  slender  prismatic  crystals,  which 
is  now  being  investigated,  and  proves  to  be  a  new  silicate  con- 
taining lead,  iron,  and  calcium  as  essential  constituents. 


292 


CLINOHEDRITE,  A   NEW  MINERAL 


The  crystallization  is  monoclinic,  and  the  crystals  are  espe- 
cially interesting  as  they  belong  to  that  division  of  the  mono- 
clinic  system  characterized  by  a  plane  of  symmetry,  but  not  an 
axis  of  symmetry,  or  to  the  class  of  crystals  called  by  Groth  * 
the  "  domatische  Klasse"  No  form  in  this  class  consists  of 
more  than  two  faces,  and  the  pinacoid  5(010)  is  the  only 
one  where  the  faces  are  parallel.  The  prevalence  of  forms 
without  parallel  faces  gives  to  the  crystals  a  peculiar  inclined- 
faced  character  or  appearance,  which  has  suggested  the  name 
of  the  mineral,  clinoliedrite  (tfXiz>en>,  incline,  and  eSpa,  face). 
Very  few  examples  of  this  kind  of  symmetry  have  been 
observed  among  mineral  substances,  the  best  being  some 
crystals  of  pyroxene  described  by  Williams,  f  Pyroxene, 
however,  generally  exhibits  the  normal  or  most  highly  devel- 
oped type  of  monoclinic  symmetry,  and  specimens  which  show 
the  lower  degree  of  symmetry  are  so  rarely  met  with  that  it 
seems  probable  that  they  are  only  the  result  of  an  accidental 
development  of  a  part  of  the  crystal  faces. 

The  crystals  of  clinohedrite  on  a  specimen  sent  to  us  by 
Mr.  Hancock  were  exceptionally  fine  and  well  adapted  for 
crystallographic  study.  They  were  about  4  mm.  long,  and 
from  2  to  3  mm.  in  diameter,  and  had  the  habit  represented 
by  Figures  1  and  2,  the  latter  being  drawn  with  the  pinacoid 


FIGURE  2. 


*  Physikalische  Krystallographie,  3.  Auflage,  p.  356,  1895. 
t  Amer.  Jour.  Sci.,  1889,  vol.  38,  p.  115. 


FROM  FRANKLIN,  NEW  JERSEY. 


293 


5(010)  in  front.  They  were  generally  attached  at  the  end 
represented  as  the  lower  one  in  the  figures,  and  the  forms  at 
that  end,  when  they  conld  be  observed,  were  rounded  and 
graded  into  one  another  so  that  it  was  difficult  to  decide  what 
ones  were  present  and  how  they  should  be  represented  in  the 
figure.  At  the  upper,  or  free  ends  of  the  crystals,  however, 
the  faces  were  exceptionally  perfect,  and  gave  beautiful 


ElGURE    3. 


FIGURE  4. 


reflections.  The  crystals  on  the  specimens  sent  by  Mr.  Nason 
were  not  so  well  suited  for  crystallographic  study,  several  of 
the  forms  being  striated  and  rounded,  and  it  was  so  difficult 
to  obtain  satisfactory  measurements  that  the  relations  of  the 
forms  did  not  become  wholly  clear  until  the  crystals  from 
Mr.  Hancock's  specimen  had  been  studied.  Some  of  the 
crystals  were  3  mm.  in  diameter,  and  Figures  3  and  4,  drawn 
in  the  same  position  as  Figure  2,  will  serve  to  exhibit  the 
curious  habit  which  they  present. 

The  position  which  has  been  adopted  seems  well  suited  for 
representing  the  forms  of  the  crystals  which  are  given  in  the 
following  table : 


6,010 

h,  320 

m,  110 

mi,  T10 


w,  120 
Z,  130 
e,  101 

el}  TOT 


tt,  TIT 

<7i,  HT 


r,  H31 

#,771 
w,  531 


o,  T31 
G!,  13T 
x,  T3T 
2/,T2T 


The  form  z,  Figures  3  and  4,  is  probably  161,  but  no  satisfac- 
tory measurements  could  be  obtained  from  it. 


294  CLINOHEDRITE,  A   NEW  MINERAL 

The  axial  ratio  was  derived  from  the  measurements  marked 
by  asterisks  in  the  accompanying  table,  and  is  as  follows : 

a  :  b  :  c  =  0.6826  :  1  :  0.3226  j  /5  =  100  A  001  =  76°  4' 

Following  is   a   list   of  measurements,  together  with   the 
calculated  angles: 


Calculated 
angle  on 

Measured 
angle  on 

Calculated. 

Measured. 

6,  010. 

6,  010. 

m  A  : 

?/?., 

110  A 

110  = 

67° 

2' 

66° 

57' 

56° 

29' 

56° 

29'* 

h  A 

A, 

320  A 

320  = 

47° 

38' 

.  . 

. 

66° 

11' 

66° 

5' 

n  A 

rc, 

120  A 

120  = 

105° 

54' 

.  . 

37° 

3' 

37° 

12' 

I  A 

^ 

130  A 

130  = 

126° 

34' 

.  . 

. 

26° 

43' 

26° 

55' 

PA 

P» 

111  A 

1T1  = 

29° 

8' 

29° 

8'* 

75° 

26' 

.  , 

,  . 

q  A 

y, 

Til   A 

TT1  = 

34° 

52' 

34° 

49' 

72° 

34' 

72° 

36' 

T  A 

>', 

331  A 

331  = 

63° 

15' 

62° 

56' 

58° 

22^ 

.  . 

S  A 

st 

551  A 

551  = 

67° 

43' 

67° 

43' 

56° 

8V 

56° 

20' 

t  A 

t, 

771  A 

771  = 

68° 

32' 

. 

55° 

44' 

. 

.  . 

^  A 

u, 

531  A 

531  = 

43° 

52' 

44° 

6' 

68° 

4' 

68° 

0' 

£  A 

X, 

T3TA 

T3T  = 

75° 

52' 

.  . 

. 

52° 

4' 

51° 

56' 

y  A 

!/, 

T2TA 

T2T  = 

54° 

56' 

.  . 

. 

62° 

32' 

.  . 

. 

jt?  A 

e, 

111   A 

101  = 

14° 

34' 

14° 

36' 

.  . 

. 

.  . 

. 

m  A 

P> 

110  A 

111  = 

51° 

54' 

51° 

54'* 

.  , 

,  . 

.  . 

. 

J9A 

?> 

111  A 

TT1  = 

58° 

37' 

58° 

29* 

.  . 

. 

.  . 

. 

2  A 

r, 

Til  A 

331  = 

36° 

21' 

36° 

20' 

.  . 

. 

.  . 

. 

r  A 

s, 

331  A 

551  = 

12° 

45' 

12° 

44' 

.  . 

. 

.  . 

. 

S  A 

t, 

551  A 

771  = 

5° 

50' 

5° 

47' 

.  . 

. 

.  . 

. 

y  A  61,  T2T  A 

TOT  = 

27° 

28' 

27°  42'         

&A 

0) 

010  A 

T31  = 

46° 

43' 

46° 

43' 

. 

.  . 

.  . 

. 

The  cleavage  is  perfect  by  parallel  to  the  pinacoid  £,010,  but 
is  not  often  observed.  The  hardness  is  5.5  and  the  specific 
gravity  3.33.  Many  of  the  crystals  are  transparent,  and  the 
color  varies  from  amethystine  to  nearly  colorless  or  white. 
The  crystals  exhibit  very  distinctly  the  phenomenon  of  pyro- 
electricity  when  tested  with  the  red  oxide  of  lead  and  sulphur 
method  described  by  Kundt.f  On  cooling  a  crystal  of  the 


*  Fundamental  angles. 

t  Ann.  d.  Phys.  u.  Chem.  xx,  p.  592,  1883. 


FROM  FRANKLIN,  NEW  JERSEY.  295 

type  represented  by  Figures  1  and  2  the  p,  e,  and  the  upper 
extremities  of  the  m  faces  in  front  became  positively  electri- 
fied and  attracted  the  particles  of  sulphur,  while  the  diagonally 
opposite  faces  #,  ?/,  pi9  e\,  and  the  lower  extremities  of  m^ 
became  negatively  electrified  and  attracted  the  red  oxide  of 
lead. 

A  section  parallel  to  the  pinacoid  (010)  when  examined  in 
polarized  light  showed  an  extinction  of  about  28°  from  the 
vertical  axis  in  the  obtuse  angle  yS,  and  this  direction  corre- 
sponds to  b.  The  plane  of  the  optical  axes  is  at  right  angles 
to  (010).  The  crystallographic  axis  b  is  the  obtuse  bisectrix, 
and  corresponds  to  C-  The  double  refraction  is  not  very 
strong,  and  is  negative. 

Material  for  the  chemical  analysis  was  first  carefully  selected 
by  hand  picking,  and  was  then  further  purified  by  pulverizing 
and  separating  by  means  of  the  barium  mercuric  iodide  solu- 
tion. That  portion  which  was  used  for  the  analysis  varied  in 
specific  gravity  between  3.344  and  3.32T. 

The  method  of  analysis  was  a?  follows :  Water  was  deter- 
mined as  loss  on  ignition,  and  the  residue,  after  fusion  with 
sodium  carbonate,  was  dissolved  in  hydrochloric  acid.  The 
solution  was  evaporated  twice  to  separate  the  silica,  and  in  the 
filtrate  from  the  silica  the  acid  was  neutralized  with  a  slight 
excess  of  ammonia,  formic  acid  of  specific  gravity  1.12  was 
added  so  as  to  make  about  one-fourth  of  the  final  volume,  and 
hydrogen  sulphide  was  passed  into  the  hot  solution  until  the 
zinc  was  precipitated.  After  filtering,  the  zinc  sulphide  was 
dissolved  in  hydrochloric  acid,  and  the  zinc  reprecipitated  as 
carbonate  and  weighed  as  oxide.  In  the  filtrate  from  the  zinc 
the  small  quantities  of  iron  and  alumina  were  precipitated 
twice  with  ammonia.  To  the  filtrates  acidified  with  hydro- 
chloric acid  bromine  was  added,  and  on  making  alkaline  and 
heating  to  boiling  all  of  the  manganese  was  precipitated,  but 
as  it  carried  a  little  calcium  it  was  redissolved,  precipitated 
from  an  acetic  acid  solution  with  bromine,  and  finally  deter- 
mined as  pyrophosphate.  Calcium  and  the  trace  of  magnesium 
were  separated  and  determined  in  the  usual  manner. 


296  CLINOHEDRITE,   A   NEW  MINERAL. 

The  results  of  the  analysis  by  Foote  are  as  follows : 


i. 

ii. 

Average. 

Ratio. 

] 

Theory  for 
32CaZuSiO6. 

Si02 

27.14 

27.29 

27.22 

0.454 

0.97 

27.92 

ZnO 

37.43 

37.46 

37.44 

0.462  ; 

|  0.469 

1.00 

37.67 

MnO 

0.49 

0.50 

0.50 

0.007  < 

CaO 

26.31 

26.19 

26.25 

0.469  j 

!  0.471 

1.00 

26.04 

MgO 

0.07 

0.08 

0.07 

0.002  i 

H20 

8.53 

8.59 

8.56 

0.476 

1.01 

8.37 

CFe,  A1VO. 

,  0.26 

0.31 

0.28 

\     ^J          /2     « 

100.32  100.00 

The  ratio  of  SiO2  :  (Zn+Mn)O  :  (Ca+Mg)O  :  H2O  is  very 
nearly  1:1:1:1,  from  which  the  formula  H2ZnCaSiO5  is  de- 
rived, in  which  the  zinc  and  calcium  are  replaced  to  a  slight 
extent  by  manganese  and  magnesium  respectively.  The 
formula  may  also  be  written  (ZnOH)(CaOH)SiO3,  and  that 
hydroxyl  is  present  is  proved  by  the  fact  that  water  is  not 
expelled  much  below  a  faint  redness.  The  formula  is  analo- 
gous to  that  of  calamine  H2Zn2SiO5  or  (ZnOH)2SiO3. 

The  pyrognostic  properties  are  as  follows  :  In  the  closed  tube 
at  a  gentle  heat  the  mineral  is  unchanged,  but  at  a  temperature 
approaching  faint  redness  it  exfoliates,  whitens  and  gives  off 
water.  Heated  before  the  blowpipe  the  mineral  exfoliates  at 
first,  and  then  fuses  at  about  4  to  a  yellowish  enamel.  A 
coating  of  zinc  oxide  is  obtained  when  the  mineral  is  heated 
alone  or  with  a  little  sodium  carbonate  on  charcoal.  The 
powdered  material  dissolves  readily  in  hydrochloric  acid,  and 
gelatinous  silica  is  obtained  when  the  solution  is  evaporated. 

In  conclusion  we  take  great  pleasure  in  expressing  our  sin- 
cere thanks  to  Messrs.  F.  L.  Nason  and  E.  P.  Hancock,  who 
have  generously  placed  at  our  disposal  all  of  the  specimens  of 
this  rare  mineral  which  they  have  been  able  to  collect. 


ON  THE  CHEMICAL  COMPOSITION  OP 
TOURMALINE. 

BY  S.  L.  PENFIELD  AND  H.  W.  FOOTE  .* 
(From  Amer.  Jour.  Sci.,  1899,  vol.  7,  pp.  97-125.) 

INTRODUCTION  AND  HISTORICAL.  —  There  is  probably  no 
common  mineral  whose  chemical  composition  has  proved  more 
perplexing  and  been  so  little  understood  as  tourmaline.  Some 
reasons  for  this  are,  first,  that  the  mineral  presents  certain 
peculiarities  in  chemical  composition  of  an  unusual  nature; 
second,  the  analysis  of  tourmaline  has  been  one  of  the  difficult 
problems  of  analytical  chemistry,  hence  reliable  data  for  the 
calculation  of  the  formula  have  not  been  easily  obtained ;  and, 
lastly,  although  good  analyses  have  been  made,  the  results  have 
not  been  thoroughly  relied  upon,  nor  have  they  been  inter- 
preted to  the  best  advantage.  The  present  investigation  was 
undertaken,  therefore,  with  the  hope  that  by  making  a  few 
analyses  with  the  utmost  possible  care  on  tourmalines  of  excep- 
tional purity,  it  would  be  possible  to  find  a  satisfactory  explana- 
tion of  the  chemical  composition  of  this  interesting  mineral. 

In  order  to  appreciate  the  problem  in  hand,  it  will  be  neces- 
sary to  review  briefly  the  work  and  the  results  of  previous  in- 
vestigators. 

The  analyses  of  Vauquelin  and  Klaproth,  made  in  the  early 
part  of  this  century,  were  naturally  defective,  because  at  the 
time  they  were  made,  lithium  was  unknown,  it  had  not  been 
discovered  that  tourmaline  contained  boron,  and  analytical 
methods  were  not  perfected. 

In  1818  the  presence  of  boron  was  detected  by  Lampardius,f 

*  NOTE.  — This  article  has  been  shortened  by  omitting  a  review  of  the  ana- 
lyses of  Rammelsberg  found  on  pp.  108-114  of  the  original  article.  —  EDITOR. 
t  Ann.  d.  Phys.  u.  Chem.,  xxx,  p.  107. 


298  THE   CHEMICAL   COMPOSITION 

and  in  the  same  year  Arfvedson  *  discovered  the  new  alkali 
metal  lithium,  and  showed  its  presence  in  spodumene,  petalite 
and  tourmaline. 

In  1827  Gmelin  f  published  analyses  of  ten  varieties  of  tour- 
maline, but  his  results  led  to  no  satisfactory  formula,  although 
the  essential  constituents  of  the  mineral,  with  the  exception  of 
the  boric  oxide,  were  determined  with  a  considerable  degree  of 
accuracy. 

In  1845  Hermann  J  published  the  results  of  four  analyses  of 
tourmaline  from  Russian  localities.  He  proved  conclusively 
that  the  iron  was  ferrous,  and  not  ferric  as  considered  by  pre- 
vious investigators.  Boric  oxide  was  not  directly  determined, 
but  estimated  by  difference,  and  the  results  compare  favorably 
with  the  direct  determinations  made  by  our  present  methods. 
He  was  the  first  to  point  out  that  silica  and  boric  oxide  are 
present  in  the  definite  molecular  proportion  4:1.  He  errone- 
ously decided  that  tourmaline  contained  carbon  dioxide,  the 
reasons  being  as  follows :  It  was  generally  believed  at  that 
time  that  the  mineral  contained  no  water,  as  stated  by  Hermann, 
"  die  Turmaline  keine  Spur  davon  enthalten"  and  it  is  true 
that  when  fragments  are  tested  by  the  usual  method  of  heating 
to  redness  in  a  closed  tube  no  water  is  obtained.  It  is  only 
when  the  material  is  heated  intensely,  best  as  fine  powder,  that 
hydroxyl  is  decomposed  and  water  given  off.  When  Hermann 
dissolved  fragments  in  a  borax  bead  he  observed  that  a  gas  was 
evolved,  and,  since  it  was  believed  that  this  could  not  be  water 
vapor,  he  supposed  that  it  must  be  carbon  dioxide.  Pains 
were  taken  to  fuse  some  of  the  mineral  in  a  tube  with  borax, 
and  to  conduct  the  gas  into  lime  water,  by  which  treatment  a 
precipitate  was  obtained  which  effervesced  with  acids,  but  it  is 
safe  to  assume  that  the  carbon  dioxide  thus  detected  was  de- 
rived from  improperly  purified  air  and  not  from  the  mineral. 

In  1850  Rammelsberg  §  published  the  results  of  the  analyses 

*  Schweigger's  Jour.  d.  Chem.  u.  Phys.,  xxii,  p.  111. 

t  Fogg.  Ann.,  ix,  p.  127. 

J  Journal  fur  prakt.  Chem.,  xxxv,  p.  232. 

§  Ann.  der  Phys.  u.  Chem.,  Ixxx,  p.  449,  and  Ixxxi,  p.  1. 


OF  TOURMALINE.  299 

of  thirty  varieties  of  tourmaline.  The  execution  of  such  a 
large  number  of  analyses  must  be  regarded  as  a  very  great 
undertaking,  since  at  that  time  gas  and  many  facilities  of  our 
modern  laboratories  were  not  available,  and  many  methods  of 
analysis  were  not  perfected.  Special  evidence  is  given  that 
great  care  was  taken  in  the  selection  of  material  for  analysis 
and  in  the  analytical  methods,  which  appear  to  have  been  well 
chosen  and  reliable  in  character.  The  analyses,  however,  were 
defective  in  several  important  particulars.  Thus  the  iron  was 
regarded  chiefly  as  ferric.  Believing,  like  Hermann,  that 
tourmaline  contained  no  water,  and  having  detected  the  pres- 
ence of  fluorine  in  some  varieties  of  the  mineral,  he  supposed 
that  the  considerable  loss  on  ignition  which  occurred  was  due 
to  the  volatilization  of  silicon  fluoride,  and  from  this  loss  he 
estimated  fluorine  to  be  present  in  amounts  varying  from  1.30 
to  2.51  per  cent.  Direct  determinations  of  boric  oxide  were 
made  in  three  cases  only,  and  in  the  remaining  analyses  this 
important  constituent  was  estimated  by  difference.  Although 
the  analyses  led  to  no  satisfactory  formula,  they  indicated  cer- 
tain prominent  characteristics  of  the  mineral,  namely,  the  great 
variation  in  the  relative  amounts  of  aluminium,  iron,  magne- 
sium and  alkalies,  and  the  nearly  uniform  amounts  of  silica 
and  boric  oxide. 

Fully  realizing  certain  defects  in  his  earlier  analyses,  Ram- 
melsberg*  published  in  1870  a  revision  of  his  former  paper. 
At  this  time  it  was  shown  that  all  varieties  of  tourmaline  con- 
tained chemically  combined  water,  and  the  amount  of  water 
was  estimated  from  the  earlier  determinations  of  the  loss  on 
ignition  after  making  certain  corrections  for  volatilization  of 
silicon  fluoride.  He  found  that  the  iron  was  chiefly  if  not 
wholly  ferrous,  and  recalculated  accordingly  his  earlier  results. 
Six  direct  determinations  of  boric  oxide  were  made,  and  it  is 
pointed  out  that  these  amounts  correspond  closely  with  the 
indirect  determinations  by  difference.  As  a  result  of  the  revi- 
sion, Rammelsberg  reached  the  conclusion  that  all  tourmalines 
are  derived  from  the  acid  H6SiO6.  In  this  he  considered  the 

*  Ann.  der  Phys.  u.  Chem.,  ccxv,  pp.  379  and  547. 


300  THE   CHEMICAL   COMPOSITION 

hydrogen  atoms  to  be  replaced  by  metals  of  different  valences, 
or,  in  other  words,  he  regarded  tourmaline  as  composed  of  a 
mixture  of  the  following  molecules : 

R'6Si06  R'    =  Na,  K,  Li,  and  H. 

R"3Si05  R"  =  Fe,  Mg,  Mn,  and  Ca. 

R'"2Si06  R'"  =  Al  and  B. 

Furthermore  he  decided  that  certain  varieties  correspond 
closely  to  the  special  formulas 

fR'8Al2BSi2010  <R'6Al12B4Si9045 

U  t  R"8Al4B2Si402o  L>  1  R"3Al12B4Si9045 

while  he  regarded  others  as  mixtures  of  these  two  molecules. 
By  substituting  hydrogen  atoms  for  the  metals  and  boron  of 
these  special  formulas,  the  acids  become  respectively  H24Si4O2o 
and  H54Si9O45,  both  of  which  are  multiples  of  H6SiO5.  He 
concluded  that  the  SiO2  and  B2O3  are  not  present  in  a  definite 
molecular  proportion,  but  that  boron  plays  the  part  of  a  metal 
and  is  isomorphous  with  aluminium. 

In  1888  Riggs  *  published  the  results  of  twenty  analyses  of 
various  types  of  tourmaline  from  American  localities.  The 
analyses  were  executed  in  the  laboratory  of  the  U.  S.  Geologi- 
cal Survey  at  Washington,  and  bear  every  evidence  of  being 
made  with  the  precision  and  care  characteristic  of  the  analyti- 
cal work  of  that  laboratory.  Boric  oxide,  water,  and  ferrous 
oxide  were  determined  directly  by  reliable  methods,  and  a  high 
degree  of  accuracy  is  claimed  for  the  analyses.  A  careful 
description  of  the  quality  of  the  material  analyzed  is  not 
given,  and  although  it  is  to  be  supposed  that  great  care  was 
taken  in  its  selection,  the  following  statement  has  left  this  in 
doubt :  "  The  analyses  do  not  represent  ideal  compounds,  but 
are  made  of  material  more  or  less  impure  .  .  .  ."  Riggs 
concludes  that  the  analyses  give  "  as  a  general  tourmaline 
formula  the  simple  boro-orthosilicate  R9BO22SiO4 "  which  is 
expressed  graphically  as  follows : 

*  Amer.  Jour.  Sci.,  1888,  vol.  35,  p.  35. 


OF  TOURMALINE.  301 

/BO, 
V        \u 


He  supposes  R  to  include  H,  Li,  Na,  K,  Ca,  Mg,  Fe,  Al,  and 
small  amounts  of  the  (A1=O)  or  possibly  (Al-OH)  radicals. 
It  may  here  be  stated  that  the  foregoing  formula  is  identical  in 
type  with  the  special  formula  R'3Al2BSi2O10  (H9BSi2O10)  of 
Rammelsberg,  and,  considering  boron  as  replacing  hydrogen 
like  a  metal,  the  silicic  acid  from  which  the  formula  is  derived 
becomes  H12Si2Oi0  or  H6SiO5.  Riggs  further  states  that,  owing 
to  slight  variations,  the  ratios  give  nearly  the  "  equally  simple 
general  formula  Ri0BO22SiO4,"  stating  that  "  between  these 
two  views  there  are  at  present  no  means  at  hand  of  deciding." 
It  would  seem,  however,  that  the  last  formula  is  impossible, 
for,  considering  hydrogen  atoms  as  replacing  R10  the  acid  can 
not  be  split  up  like  other  oxygen  acids  into  silicic  and  boracic 
anhydrides  and  water.  There  are  also  given  the  following 
special  formulas  for  three  pronounced  types  of  tourmaline  : 

I.  Lithia  tour.     12Si02  .  3B203  .  4H20  .  8A1203  .  2(Na,Li)20. 
II.  Iron  tour.        12Si02  .  3B203  .  4H2O  .  7A1203  .  4FeO  .  Na2O. 
III.  Mg  tour.         12Si02  .  3B203  .  4H20  .  5A1203  . 


By  substituting  hydrogen  atoms  for  the  metals  in  these  spe- 
cial formulas  we  obtain  : 

I.  and  II.   H60B6Si12063  or  H20B2Si4021. 
III.         H58B6Si12062  or  H19*  B2Si4O20|. 

Soon  after  the  appearance  of  Riggs'  article,  Wulfing  *  recal- 
culated the  results  of  these  twenty  analyses  and  concluded  that 
all  tourmalines  may  be  regarded  as  isomorphous  mixtures  of 
two  aluminium  silicates,  "Alumosilicate"  of  the  following 
composition. 

I.   Alkali  tourmaline         12SiO2  .  3B203  .  8A1203  .  2Na20  .  4H20. 
II.   Magnesia  tourmaline     12Si02  .  3B203  .  5A1303  .  12MgO  .  3H20. 

*  Mineralogische  und  petrographische  Mittheilungen,  x,  p.  161. 


302  THE   CHEMICAL    COMPOSITION 

In  these  formulas  it  is  assumed  that  the  isomorphous  ele- 
ments K  and  Li  replace  the  Na ;  Fe'"  the  Al ;  and  Fe",  Mn 
and  Ca  the  Mg.  By  substituting  hydrogen  atoms  for  the 
metals  in  the  foregoing  formulas  it  is  found  that  they  both  are 
derivatives  of  the  same  acid,  H60B6Si12O63  or  H20B2Si4O2i.  The 
conclusions  derived  by  Wiilfing  are  that,  although  in  most 
cases  the  results  of  the  analyses  agree  with  the  percentage 
values  calculated  from  his  formulas,  the  agreement  is  not 
always  satisfactory.  This  he  ascribes  to  the  possible  need  of 
a  third  formula ;  to  possible  inaccuracies  in  the  difficult  ferrous 
iron  determinations ;  and  in  part  to  the  fact,  as  stated  by  Riggs, 
that  "the  analyses  do  not  represent  ideal  compounds.  .  .  ." 
He  therefore  considers  it  necessary  that  further  analyses  of 
more  carefully  selected  materials  should  be  made. 

At  about  this  time  also  Scharizer  *  published  analyses  of 
three  varieties  of  tourmaline  from  Schiittenhofen,  Bohemia, 
and  discussed  his  results  in  connection  with  the  analyses  of 
Riggs.  His  final  conclusion  is  that,  with  the  exception  of  the 
green  varieties,  tourmalines  possess  a  chemical  constitution 
which  can  be  expressed  by  the  general  formula : 

[E2Rj2[R3R2]4Al8(Si03)12[(BO,HO,F)2]7. 

This  formula  is  certainly  difficult  to  comprehend,  and  if  we 
understand  it  correctly,  the  univalent  radicals  BO  and  HO  are 
isomorphous  with  fluorine,  and  these  constituents,  taken  twice, 
can  replace  oxygen. 

In  1889  Jannasch  and  Kalb  f  published  the  results  of  nine 
tourmaline  analyses,  in  which  the  water  and  boron  were  deter- 
mined directly.  These  investigators  derived  from  their  anal- 
yses the  general  formula  R9  .  BO2  .  (SiO4)2,  for  which  the 
following  structural  formula  was  proposed : 

*  Zeitschr.  fur  Kryst.,  XT,  p.  343. 

t  Berichte  der  deutschen  chemischen  Gesellschaft,  vol.  xxii,  p.  216.  Also 
Inaugural  Dissertation,  Geo.  W.  Kalb,  Gottingen. 


OF   TOURMALINE.  303 


This  formula,  R9  .  BO2  .  (SiO4)2,  is  identical  with  the  one  pro- 
posed by  Riggs,  and  essentially  like  the  special  formula 
R'3Al2BSi2O10  of  Rammelsberg.  The  following  special  for- 
mulas are  also  given  : 

I.  Li  tour.          24SiO2  .  6B2O3  .  15A12O3  .  4FeO  .  4(Li2O,  Na2O)  .  7H2O 
II.  Fe  tour.          24SiO2  .  6B2O3  .  14A12O3  .  9FeO  .  2Na2O  .  7H2O 
III.  Fe-Mg  tour.  24SiO2  .  6B2O8  .  ISA^Og  .  12MgO  .  2^0  .  7H2O 


These  special  formulas  in  their  general  type  are  similar  to 
those  proposed  by  Riggs.  By  substituting  hydrogen  atoms 
for  the  metals  they  all  reduce  to  one  and  the  same  acid, 
H120Bi2Si24O126  or  H20B2Si4O21. 

There  is  evidence  that  Jannasch  does  not  place  great  con- 
fidence in  the  foregoing  formulas,  for  in  Hintze's  Mineralogy* 
the  composition  is  expressed  as  follows  : 

I.   Lithia  tourmaline  Sii20«8B6Al16(Na,  Li)4H7 

II.  Iron  tourmaline  Si12067^B6Al14Fe9Na2H7 

III.  Magnesia  tourmaliue  Si12069B6Al13Mg12Na2H7 

These  formulas  are  essentially  different  from  the  ones  first  pro- 
posed, which  may  readily  be  seen  by  substituting  hydrogen 
atoms  for  the  metals  and  comparing  the  resulting  acids,  as 
follows  : 

I.   H56B6Si12063    or  H18iB2Si4021 

II.  H69B6Si12067i  or  H23B2Si4022i 

III.   H72B6Si12069    or  H24B2Si4023 

Soon  after  the  appearance  of  the  articles  of  Riggs  and  of 
Jannasch  and  Kalb,  the  results  of  their  analyses  were  recalcu- 

*  Vol.  ii,  p.  311  (communication  by  manuscript  from  Jannasch). 


304  THE   CHEMICAL   COMPOSITION 

la  ted  by  Goldschmidt,*  and  the  conclusion  was  reached  that 
tourmaline  may  be  regarded  as  containing  the  two  following 
molecules : 

I.  Alkali  tourmaline  R'32R<'"66Si3iOi62 

II.  Magnesia  tourmaline       R'zoR'^R"^^^^ 

These  formulas  are  both  derived  from  an  acid  H200Si31Oi62  or 
H6.46SiO5.23. 

In  1893  Rheineck,f  after  calculating  the  results  of  the  many 
tourmaline  analyses,  concluded  that  the  composition  of  all 
tourmalines  may  be  expressed  by  formulas  of  the  following 
type,  in  which  A14  appears  as  a  constant : 

I.   Alkali  tourmaline  Al4Si3BH3Oi5 

II.  Alkali  tourmaline  Al4Si3B2H4Oi7 

III.  Magnesia  tourmaline          Al4Si5B2M4H4025,  etc. 

M  represents  the  bivalent  metals  Fe,  Mn,  Mg  and  Ca.  H 
includes  Na,  Li,  and  K.  Among  the  numerous  examples  he 
stated  that  the  composition  of  the  black  tourmaline  from 
Pierrepont,  N.  Y.,  may  be  represented  by  either  of  the  follow- 
ing expressions : 

1UA1  Si  B  M  H  O  ( l°A14SisB2H6018 

114Al4bi5b2M4M4U25  \    „  .,  ~. 

10  A  1    Qi    -R  O  1  y^A14^15^2^L4ll4U25 

IOA14S18B6026  (21Al4Si5B4M4026 

By  substituting  hydrogen  atoms  for  the  metals  in  these  ex- 
pressions, and  multiplying  by  the  factors,  114  and  10  in  the 
one  case,  and  10,  93  and  21  in  the  other,  the  acids  become 
HasseBzssSieooOgioo  an(^  HM82B2eoSi66oO80B1,  or,  when  simplified 
Hi9.oB1.9Si4O2o.6  and  H18.9B1.9Si4O20.3.  The  improbable  nature  of 
such  acids  is  evident.  In  the  opening  paragraph  of  his  article, 
Rheineck  stated  that  the  obscure  and  complex  chemical  rela- 
tions of  this  mineral  have  necessitated  a  series  of  speculations 
and  calculations  extending  somewhat  interruptedly  over  a 
period  of  many  years,  in  order  to  arrive  at  results  such  as 
those  embodied  in  the  foregoing  formulas. 

*  Zeitschr.  fiir  Kryst.,  xvii,  pp.  52  and  61. 
t  Zeitschr.  fur  Kryst.,  xxii,  p.  52. 


OF  TOURMALINE. 


305 


In  1895  Clarke*  discussed  the  constitution  of  tourmaline 
and  proposed  the  following  formulas : 


l. 


Al—  Si04=Al 

\Si04=Al—  B0a 

Al—  B03:=  NaH 

/Si04=Al—  B02 
Al—  Si04=Al 


2. 


Al—  Si04= 

\Si04=Al—  B02 


Al—  B08=] 

/Si04=Al—  B02 

Al—  Si0=Al 


3. 

/Si04EEMgH 
Al—  SiO^MgH 
\Si04=Al—  B02 


Al—  B0= 


i04=Al—  B02 
Al—  Si04= 


Al—  Si04= 

\Si04=Al—  B02 


Al—  B03= 
Si04=iAl—  B0 


Al—  Si0= 


Clarke  assumes  variations  from  these  formulas  in  that  Fe'" 
and  Cr  can  replace  the  Al;  Fe"  and  Mn  the  Mg;  Ca  the 
NaH  and  small  amounts  of  F  the  BO2.  Proof  of  a  consti- 
tution corresponding  to  the  formulas  cannot  of  course  be 
expected,  but  it  is  doubtful  whether  aluminium  could  exercise 
such  varied  functions  as  the  formulas  indicate.  The  grounds 
for  believing  that  fluorine  can  replace  BO2  are  not  stated.  The 
acid  from  which  all  these  formulas  are  derived  is  H29B3Si6O31 
or  H19.33B2Si4O20.66. 

Lastly  Grothf  has  adopted  the  formula  of  Jannasch 
[SiO4]2  .  BO2  .  K/9,  but  interprets  it  as  follows : 

*  Bulletin  of  the  U.  S.  Geological  Survey,  No.  125,  p.  56. 

t  Tabellarische  Uebersicht  der  Mineralien,  4te  Auflage,  1898,  117. 


20 


306  THE   CHEMICAL   COMPOSITION 

Si  Si 

/A\        /A\ 
OOOO    0000 


ERK    Al    KEK, 

A 


B=0 

or  [Si04]2[A10 .  BO]  [(A10)2)  Mg,  Fe,  Na2,  Li,,  H2]3 

That  the  uiiivalent  radical  (A1O)  can  replace  R'  does  not 
appear  in  the  original  article  of  Jannasch,  and  it  makes  a 
decided  difference  whether  three  R's  are  replaced  by  one  atom 
of  Al  or  by  three  [A1O]  radicals.  The  latter  assumption 
implies  a  basic  character  which  tourmaline  does  not  possess. 

We  have  thus  reviewed  the  work  already  done  in  order  to 
show  the  difficulties  which  this  problem  has  presented.  It  is, 
however,  interesting  to  note  how  closely  different  investigators 
come  to  one  type  of  acid  from  which  all  varieties  of  tourma- 
line are  derived.  For  the  sake  of  comparison  these  acids  have 
been  reduced  to  four  silicon  atoms,  and  are  given  below,  both 
as  borosilicic  acids  and  with  the  boron  replaced  by  hydrogen. 

Bammelsberg  {  J^^  £  £££  =  HeSi°6 

•H18B2Si4020        or  H24Si4020 

H20B2Si4020        or  H26Si4020  (Irrational) 

"  H20B2Si4021        or  H26Si4021 

,  T,  .,   ( H18B2Si4020         or  H24Si4020 
Jannasch  and  Kalb  1  TT ™   *.  *  -„-  Q.  n 

(H20B2Si4O21         or   H26bi4(J21 

Wtilfing  H20B4Si4O21        or  H26Si4021 

Goldschmidt  H25.8Si4020.9 

(  H19.0B1.9Si4020.6  or  H24.7Si4020.6  (Irrational) 

(  H18.9B1.9Si202o.3  or  H24.6Si4020.3  etc. 

Clarke  H19.33B2Si4020.66  or  H25.33Si4020.65 

Method  of  analysis.  —  The  present  investigation  was  under- 
taken with  the  expectation  that  for  the  solution  of  the  problem 
in  hand  it  would  probably  not  be  necessary  to  make  a  long 


OF  TOURMALINE.  307 

series  of  analyses  but  rather  exceedingly  accurate  analyses  of  a 
few  carefully  selected  types  of  tourmaline.  We  therefore 
prefaced  our  work  by  a  careful  study  of  those  features  of  the 
tourmaline  analysis,  which  have  proved  most  difficult.  The 
method  proposed  by  Gooch*  of  distilling  off  the  boron  with 
methyl  alcohol  and  weighing  it  as  calcium  borate  is  very  exact, 
but  its  application  to  an  insoluble  silicate,  especially  one  con- 
taining fluorine,  needed  careful  study.  Mixtures  were  accord- 
ingly made  of  silicates  to  which  weighed  quantities  of  borax 
and  fluorite  were  added  and  the  following  conditions  were 
determined,  which  yielded  the  most  accurate  boron  determina- 
tions. The  mineral  was  fused  with  from  four  to  five  parts  of 
sodium  carbonate,  the  fusion  extracted  with  water,  and,  with- 
out filtering,  an  excess  of  ammonium  carbonate  was  added. 
The  insoluble  residue  and  the  precipitate  were  filtered  off,  the 
filtrate  concentrated,  acidified  slightly  with  nitric  acid  and 
distilled  with  methyl  alcohol.  The  residue  from  the  sodium 
carbonate  fusion,  together  with  the  precipitate  produced  by 
the  ammonium  carbonate,  was  fused  again  with  sodium  car- 
bonate, treated  with  water,  filtered  and  distilled  with  methyl 
alcohol  after  acidifying  with  nitric  acid.  About  one  half  of 
one  per  cent  of  boric  oxide  was  obtained  from  the  second  treat- 
ment, and  in  no  case  did  we  succeed  in  obtaining  an  exact  de- 
termination of  the  boric  oxide  without  repeating  the  fusion. 
The  weighed  mixture  of  calcium  borate  and  oxide  was  in  all 
cases  found  to  contain  a  small  amount  of  fluorine.  It  was 
therefore  dissolved  in  hydrochloric  acid,  and  part  of  the  lime 
together  with  calcium  fluoride  was  precipitated  with  sodium 
carbonate.  The  precipitate  was  ignited,  treated  with  acetic 
acid  and  the  resulting  calcium  fluoride  weighed.  The  amount 
of  fluorine  thus  found  never  amounted  to  over  0.20  per  cent. 

Fluorine  was  determined  by  the  modified  Berzelius  method 
described  by  Penfield  and  Minor,  f 

Water  was  determined  by  fusing  the  mineral  with  sodium 
carbonate  in  a  combustion  tube  and  collecting  the  water  in  a 

*  Amer.  Chem.  Jour.,  ix.  p.  23. 
t  Page  232. 


308  THE  CHEMICAL   COMPOSITION 

weighed  tube  containing  sulphuric  acid,  a  method  which  has 
been  thoroughly  tested  and  is  known  to  give  reliable  results.* 

For  the  determination  of  the  bases  the  mineral  was  decom- 
posed by  fusion  with  sodium  carbonate  and  the  silica  separated 
as  usual.  It  was  found  by  experiment  that  the  amount  of 
silica  volatilized  by  the  small  amount  of  fluorine  in  the  min- 
eral could  practically  be  neglected.  In  one  variety  of  tourma- 
line two  determinations  of  silica  made  by  the  Berzelius  method 
of  fusing  the  mineral  and  a  weighed  amount  of  silica  with 
sodium  carbonate,  and  separating  the  silica  with  ammonium 
carbonate  and  an  ammoniacal  solution  of  zinc  oxide,  gave 
36.69  and  36.76  per  cent,  while  determinations  by  the  ordi- 
nary method  gave  36.75  and  36.73  per  cent.  A  similar  con- 
clusion, that  when  the  amount  of  fluorine  is  small  it  is  not 
necessary  to  separate  the  silica  by  the  Berzelius  method,  was 
also  reached  by  Riggs. 

The  filtrate  from  the  silica  was  evaporated  to  dryness,  mois- 
tened with  hydrochloric  acid  and  repeatedly  evaporated  with 
methyl  alcohol  to  remove  all  possibilities  of  boric  oxide  being 
precipitated  with  the  bases  and  thus  increasing  their  weight. 

For  the  determination  of  the  alkalies  the  Smith  fusion  was 
employed  and,  after  removal  of  ammonium  salts,  the  residue 
was  treated  with  acid  and  methyl  alcohol  and  evaporated  to 
remove  any  borate  that  might  possibly  be  present.  Lithium 
was  separated  by  the  Gooch  method  of  boiling  with  amyl 
alcohol,!  and  was  finally  weighed  as  sulphate. 

It  was  proved  by  careful  qualitative  tests  J  that  the  iron 
was  ferrous,  and  that,  at  the  most,  not  more  than  traces  of 
ferric  iron  could  be  present.  This  statement  holds  good  not 
only  for  the  varieties  analyzed,  but  for  all  the  varieties  of 
black  tourmaline  which  were  accessible  to  us. 

Selection  and  preparation  of  material.  —  One  of  the  varieties 
selected  for  analysis  was  the  white  or  colorless  tourmaline 
from  De  Kalb,  St.  Lawrence  Co.,  New  York.  This  was  chosen 

*  Amer.  Jour.  Sci.,  1894,  vol.  48,  p.  31. 

t  Amer.  Chem.  Jour.,  ix,  p.  33. 

t  Amer.  Jour.  Sci.,  1899,  vol.  7,  p.  124 


OF  TOURMALINE.  309 

because  according  to  the  analysis  of  Riggs  it  represented 
almost  the  extreme  type  of  a  magnesia  tourmaline,  and,  con- 
taining almost  no  iron,  there  could  be  no  appreciable  error 
from  a  failure  to  estimate  that  constituent  correctly.  The 
material  was  derived  in  part  from  a  specimen  in  the  Brush 
Collection  and  in  part  from  specimens  collected  by  one  of  us 
(Penfield)  while  connected  with  the  U.  S.  Geological  Survey. 
The  clear,  colorless,  glassy  material  was  most  carefully  se- 
lected with  the  aid  of  a  lens,  ground  and  sifted  to  a  uniform 
grain,  and  suspended  in  methylen  iodide.  The  specific 
gravity  was  uniform,  and  the  portion  used  for  the  analysis 
floated  at  3.065  and  sank  at  3.033.  As  an  additional  pre- 
caution the  grains  were  treated  with  a  mixture  of  hydro- 
chloric and  hydrofluoric  acids,  which  have  almost  no  action 
even  on  finely  pulverized  tourmaline,  in  order  to  remove  any 
possible  traces  of  adhering  calcite,  tremolite  or  pyroxene,  al- 
though these  were  not  seen  nor  believed  to  be  present.  It 
may  be  stated  concerning  the  final  product  that  probably  it 
was  as  pure  as  it  is  possible  to  get  a  mineral  substance. 

Another  variety  selected  for  analysis  was  from  the  feldspar 
quarries  at  Haddam  Neck  on  the  Connecticut  River.  Won- 
derful tourmalines  have  recently  been  obtained  from  this 
locality,  and  they  are  already  well  known  to  most  collectors. 
We  are  indebted  for  our  supply  of  material  to  Mr.  Ernest 
Schernikow  of  New  York,  who  generously  placed  at  our  dis- 
posal an  almost  unlimited  supply  of  crystals  of  gem  quality. 
We  selected  small  prisms,  2  to  4  mm.  in  diameter,  of  a  uni- 
form rather  pale  green  color.  They  were  of  ideal  purity, 
perfectly  transparent  and  without  flaws.  Any  traces  of 
foreign  material  that  might  possibly  be  adhering  to  their  outer 
surfaces  were  removed  by  treating  them  for  a  considerable 
time  with  hydrofluoric  acid.  The  specific  gravity,  taken  with 
the  chemical  balance,  was  found  to  be  3.089. 

We  were  prepared  to  extend  our  investigation  by  analyzing 
other  varieties,  but  having  completed  the  above  mentioned 
two  and  finding  that  the  results  corresponded  with  those  of 
other  investigators,  it  was  decided  that  the  data  which  would 


310 


THE   CHEMICAL   COMPOSITION 


be  derived  from  further  analyses  would  probably  add  very 
little  to  the  knowledge  which  we  already  possess. 
The  results  of  the  analyses  are  as  follows : 

COLORLESS  TOURMALINE,  DE  KALB,  N.  Y. 


I. 

II. 

Average. 

Riggs. 

Si02 

36.69 

36.76 

36.72  - 

-60 

0.612          4.00        36.88 

Ti02 

0.06 

0.05 

0.05 

0.12 

BA 

10.86 

10.77 

10.81  - 

-70 

0.154          1.01        10.58 

A1203 

29.75 

29.61 

29.68  - 

-17 

=  1.741  1                                   28.87 

FeO 

0.23 

0.21 

0.22- 

-36 

=  0.006 

0.52 

MgO 

14.91 

14.92 

14.92  - 

-20 

=  0.746 

14.53 

CaO 

3.47 

3.50 

3.49- 

-28 

=  0.125 

3.042        19.90          3.70 

Na20 

1.29 

1.23 

1.26- 

-31 

-  0.040 

1.39 

K20 

0.07 

0.03 

0.05- 

-47 

=  0.002 

0.18 

H2O 

2.98 

.  .  . 

2.98- 

-    9 

=  0.331 

3.56 

F 

0.92 

0.95 

0.93- 

-19 

=  0.049 

0.50 

101.11 

100.83 

0  equivalent  to  F 

0.39 

0.21 

100.72 

100.62 

GREEN  TOURMALINE,  HADDAM  NECK,  CONN. 

I. 

n. 

Average. 

Brazil. 

Riggs. 

Si02 

36.87 

37.05 

36.96  - 

-60 

0.616          4.00        37.39 

Ti02 

0.03 

0.03 

0.03 

? 

B208 

11.09 

10.92 

11.00  - 

-70 

0.157          1.02        10.29 

A1203 

39.53 

39.59 

39.56  - 

-17 

=  2.327 

39.65 

FeO 

2.12 

2.15 

2.14- 

-36 

=  0.059 

*2.42 

MnO 

1.96 

2.04 

2.00- 

-  35.5  =  0.056 

1.47 

MgO 

0.15 

0.15 

0.15- 

-20 

=  0.008 

none 

CaO 

1.32 

1.25 

1.28- 

-28 

=  0.046 

•  3.078        19.98          0.49 

Na20 

2.13 

2.06 

2.10- 

-31 

=  0.068 

12.67 

Li2O 

1.65 

1.63 

1.64- 

-15 

=  0.110 

1.71 

H20 

3.14 

3.06 

3.10- 

-    9 

=  0.344 

3.63 

F 

1.09 

1.17 

1.13- 

-19 

=  0.060 

0.32 

101.09 

100.04 

O  equivalent  to  F 

0.48 

0.13 

100.61 

99.91 

On  treating  the  analyses  according  to  the  customary  method 
of  deriving  a  formula  (dividing  each  constituent  by  its  molec- 
ular weight  and  finding  the  ratio  of  the  quotients)  it  was 


*  Includes  0.15  per  cent  Fe203. 


t  Includes  0.25  per  cent  K2O. 


OF  TOURMALINE.  311 

found  that  although  the  SiO2  and  B2O3  were  present  in  the 
proportion  of  4  :  1,  no  definite  relation  could  be  detected 
between  the  silica,  the  different  kinds  of  oxides,  and  the  water. 
It  was  decided,  therefore,  to  determine  the  relative  number 
of  hydrogen  atoms  equivalent  to  the  metals  and  thus  learn 
the  acid  from  which  tourmaline  is  derived.  This  was  readily 
accomplished  by  dividing  the  constituents  by  appropriate 
fractions  of  their  molecular  weights ;  for  example,  since  the 
aluminium  atoms  in  A12O3  replace  six  hydrogens,  the  quantity 
of  A12O8  was  divided  by  one  sixth  of  its  molecular  weight, 
the  FeO  by  one  half  of  its  molecular  weight,  etc.  Since 
fluorine  is  regarded  as  playing  the  same  role  as  hydroxyl,  its 
ratio  was  added  directly  to  that  of  the  hydrogen.  The  result 
of  this  treatment  is  very  satisfactory.  The  first  analysis  gives 
the  ratio  of  SiO2  :  B2O8  :  H  =  4  :  1  :  19.90,  and  the  second 
4  :  1.02  :  19.98.  Both  ratios  approximate  so  closely  to 
4:1  :  20  that  there  can  be  no  reasonable  doubt  that  the  acid 
from  which  these  tourmalines  are  derived  is  H^B^i^.^. 
This  formula  may  seem  at  first  somewhat  complex,  but  it  is 
not  especially  so  for  a  boro-silicic  acid.  It  cannot  be  simpli- 
fied by  division,  and  it  is  based  upon  the  very  best  kind  of 
evidence,  namely,  the  close  approximation  to  rational  numbers 
of  the  two  ratios,  which  are  derived  from  widely  separated 
types  of  tourmaline. 

Before  discussing  the  possible  constitution  of  this  acid,  it 
will  be  shown  to  what  extent  the  analyses  of  other  investiga- 
tors confirm  the  results  obtained  by  us. 

Review  of  the  Analyses  of  Riggs.  —  Twenty  analyses  of 
American  tourmalines  were  made  by  Riggs,  and  the  ratios 
derived  from  them  furnish  the  very  best  evidence  of  the 
accuracy  of  his  results.  The  ratios  are  given  on  page  312. 
The  average  of  the  ratios  is  4  :  0.95  :  19.88,  or  a  very  close 
approximation  to  4  :  1  :  20,  which  indicates  that  tourmaline  is 
derived  from  the  acid  H20B2Si4O21.  It  is  pointed  out  by 
Riggs  that  "  the  boric  acid  found  invariably  falls  short  of  the 
theory."  This  is  generally,  though  not  always,  the  case, 
and  it  is  presumed  that  this  slight  defect  in  the  analyses  is 


312 


THE   CHEMICAL   COMPOSITION 


Total 


Total 


No.* 

Si03 

:      B203 

hydrogen. 

No. 

SiOa 

B203 

hydrogen. 

36. 

4 

0.90 

20.2 

46. 

4 

0.96 

20.2 

37. 

4 

0.93 

20.5 

47. 

4 

0.98. 

20.08 

38. 

4 

0.92 

19.5 

48. 

4 

1.01 

20.06 

39. 

4 

0.94 

19.7 

49. 

4 

1.01 

20.12 

40. 

4 

0.96 

19.3 

50. 

4 

0.98 

19.2 

41. 

4 

0.92 

19.7 

51. 

4 

0.91 

19.6 

42. 

4 

0.97 

19.8 

52. 

4 

0.94 

20.11 

43. 

4 

0.94 

20.03 

53. 

4 

0.97 

18.9 

44. 

4 

0.88 

20.2 

54. 

4 

0.98 

19.8 

45. 

4 

0.95 

20.03 

55. 

4 

1.01 

20.6 

due  to  the  fact  that  it  is  not  always  possible  to  obtain  a 
correct  determination  of  boric  oxide  by  the  Gooch  method 
without  a  second  fusion  of  the  silicate  with  sodium  carbonate, 
which  Riggs  does  not  mention  having  made.  It  is  not  indicated 
by  the  ratios  that  these  analyses  "  give  as  a  general  tourmaline 
formula  the  simple  boro-orthosilicate  R9B022SiO4"  suggested 
by  Riggs.  The  nearest  approach  to  this  is  analysis  No.  53,  in 
which  the  ratio  of  SiOa  to  the  total  hydrogen  is  4  :  18.9. 
The  ratios  with  few  exceptions  show  a  very  close  approxima- 
tion to  the  rational  numbers  4:1:  20.  In  eleven  cases  the 
numbers  for  the  hydrogen  ratios  vary  between  the  narrow 
limits  19.8  and  20.2.  How  exact  the  analyses  must  be  in 
order  to  yield  such  ratios  may  be  best  understood  when  it  is 
known  that  a  difference  of  one-half  of  1  per  cent  in  the 
estimation  of  either  silica  or  water  would  change  the  numbers 
of  the  hydrogen  ratio  ±  0.27  in  the  one  case  and  ±  0.38  in 
the  other.  If  the  silica  were  one-half  of  one  per  cent  high 
and  the  water  correspondingly  low,  the  effect  upon  the  ratio 
would  be  to  change  it  from  4  :  1  :  20  to  4  :  0.99  :  19.35. 
The  evidence  is  therefore  convincing  that,  with  the  excep- 
tion of  analysis  No.  53  (brown  tourmaline  from  Gouverneur, 
N.  Y.),  the  analyses  of  Riggs  are  very  exact,  and  also  that 

*  The  numbers  correspond  to  those  given  on  page  555  of  the  Sixth  Edition 
of  Dana's  Mineralogy,  where  the  analyses  of  Riggs  are  tabulated.  The  same 
holds  true  for  other  analyses,  cited  on  pp.  313,  314,  and  315. 


OF  TOURMALINE. 


313 


the  material  he  analyzed  was  very  pure.*  Leaving  out  of 
consideration  this  one  analysis,  which  may  be  considered  as 
either  defective  or  made  upon  impure  material,  the  average  of 
the  ratios  of  Riggs's  analyses  becomes  4  :  0.95  :  19.91. 

The  analyses  of  Riggs  were  very  severely  criticized  by 
Rammelsberg,  who  characterized  tourmaline  analysis  as  "  kein 
Thema  fur  Anf anger"  but  in  the  light  of  our  present  inves- 
tigation we  find  the  results  very  accurate,  and  it  may  justly  be 
said  that  we  are  indebted  to  Riggs  for  the  best  series  of  tour- 
maline analyses  that  has  ever  been  made.  In  fact,  our  conclu- 
sions regarding  the  composition  of  the  mineral  might  readily 
have  been  deduced  from  his  results  alone. 

Review  of  the  Analyses  of  Jannasch  and  Kail}.  —  Nine  an- 
alyses were  made,  from  which  the  following  ratios  have  been 


ucuiaiea 

No.  t  SiO2 

B203 

Total 
hydrogen. 

No. 

Si02 

B203 

Total 
hydrogen. 

'56.    4 

0.96 

19.7 

61. 

4 

0.95 

20.2 

57.     4 

0.99 

19.8 

62. 

4 

0.80 

20.00 

58.     4 

0.95 

20.4 

63. 

4 

0.98 

19.7 

59.     4 

0.92 

18.8 

64. 

4 

0.84 

20.01 

60.     4 

0.88 

20.4 

Average 

4 

0.92 

19.9 

These  analyses,  like  those  of  Riggs,  bear  every  evidence  of 
having  been  made  with  great  precision,  and  the  ratios,  with  the 
single  exception  of  No.  59,  approximate  closely  to  4  :  1  :  20, 
thus  furnishing  additional  evidence  that  the  acid  from  which 
all  tourmalines  are  derived  is  H20B2Si4O2i.  The  analyses  do 
not  indicate  the  general  formula  R9  .  BO2 .  2SiO4,  proposed  by 
Jannasch  and  Kalb.  Their  boric  oxide  determinations  are  in 
all  cases  a  trifle  too  low  for  the  theory,  but  it  is  believed  that 
the  reason  for  this  is  to  be  sought  in  imperfections  of  the 

*  In  a  personal  communication  from  Professor  Riggs  the  following  state- 
ment is  made  concerning  the  quality  of  the  material  investigated  by  him : 
"  The  material  analyzed  was  of  excellent  quality,  selected  with  great  care. 
The  colorless,  pink  and  light  green  varieties  were  transparent,  gem-like  crys- 
tals, and  the  material  of  the  rose-colored,  brown  and  black  varieties  was,  in 
my  opinion,  equally  pure."  Dated,  Hartford,  January  4th,  1899. 

t  See  p.  312. 


314  THE   CHEMICAL   COMPOSITION 

method  *  for  determining  this  constituent  in  a  complex  silicate. 
The  analyses  are  excellent,  and  they  rank  with  those  of  Riggs, 
among  the  best  analyses  of  tourmaline  that  have  been  made, 
From  our  own  experience,  however,  it  is  very  questionable 
whether  tourmaline  contains  so  much  ferric  iron  as  recorded 
in  some  of  these  analyses  (2.90  to  6.68  per  cent). 

The  Analyses  of  Scharizer.  —  The  ratios  of  the  three  analy- 
ses are  as  follows : 


No.t 

Si02    : 

B203 

Total 
:  hydrogen. 

65..  . 

.  .  4     : 

0.70 

:     20.9 

66..  . 
67  . 

.   .  4     : 
4     : 

0.76 
0.74 

:      21.0 

:     20.2 

By  comparing  these  ratios  with  the  ones  which  have  been  pre- 
viously considered,  it  would  seem  that  there  are  good  grounds 
for  believing  that  in  these  analyses  the  B2O8  determinations  are 
too  low,  and  that  the  bases  have  not  been  determined  with 
extreme  accuracy.  The  ratios  of  SiO2  to  the  total  hydrogen 
atoms  in  the  main  substantiate  the  formula  H20B2Si4O21. 

Analyses  from  Miscellaneous  Sources.  —  In  looking  over  the 
literature  a  number  of  analyses  have  been  found  which  need 
to  be  recorded.  They  have  been  made  partly  for  the  purpose 
of  identifying  the  mineral  and  partly  for  the  purpose  of  deter- 
mining the  character  of  the  tourmaline  from  special  localities, 
but  none  of  them  have  been  made  for  the  special  purpose  of 
determining  the  chemical  composition  of  the  species.  It  seems 
sufficient  to  give  the  ratios  only,  page  315. 

As  indicated  by  the  variations  in  the  ratios,  the  analysts 
apparently  have  not  had  sufficient  experience  to  enable  them 
to  deal  successfully  with  such  a  difficult  problem  as  the  tourma- 
line analysis.  The  average  of  the  ratios,  however,  approxi- 
mates to  4  :  1  :  20  and  thus  substantiates  our  formula. 

Titanium  in  tourmaline.  —  Titanium  seems  to  have  been 
overlooked  in  the  earlier  analyses  of  tourmaline,  but  is  reported 
in  several  of  the  analyses  of  Riggs,  Jannasch  and  Kalb,  and 
others.  The  quantity,  however,  has  always  been  found  to  be 

*  Bodewig,  Zeitschr.  fur  Kryst.,  viii,  p.  211,  1883.  t  See  p.  312. 


OF  TOURMALINE,  315 

Total 
No.  *  Locality.  Analyst.  Si02  :     B2O3        :  hydrogen. 

69.   Mt.  Bischoff    ,  .  Sommerland          .  4 


70.  Campolongo     Engelrnann   ....  4 

71.  Sysersk,  Urals    ....  Cossa  and  Arzruni  4 

72.  Montgomery  Co.,  Md.  Chatard 4 

73.  Nevada  Co.,  Cal.  .  .  .  Melville 4 


74.  Tamaya,  Chili    ....  Schwarz 4 

75.  Straschin,  Bohemia    .  Weisner 4 

76.  Urulza,  Siberia  ....  Stchusseff 4 

77.  Kolar,  India Chapman  Jones     .  4 

Average    ...  4 


0.98 
0.82 
0.89 
0.84 


1.02 
1.10 

0.85 
0.87 
0.92 


18.5 
17.4 
18.8 
20.4 
20.8 
19.1 
19.4 
19.0 
19.1 
19.2 


small,  amounting  to  over  one  per  cent  (reckoned  as  TiO2)  in 
only  four  of  the  analyses  and  to  over  0.6  per  cent  in  but  two 
others.  It  has  not  been  taken  into  consideration  in  making 
the  foregoing  calculations,  partly  because  it  would  exert  no 
appreciable  influence  on  the  final  result,  but  chiefly  because 
it  is  uncertain  whether  the  titanium  in  this  mineral  plays 
the  part  of  a  tetravalent  element  replacing  silicon,  or  of  a 
trivalent  element  replacing  aluminium.  Although  it  may  not 
be  possible  with  the  data  now  at  hand  to  definitely  settle 
this  question,  still  the  analyses  furnish  some  evidence  that 
the  element  should  be  regarded  as  trivalent.  This  result 
has  been  reached  by  considering  titanium  both  as  TiO2 
replacing  SiO2  and  as  Ti2O3,  replacing  A12O3,  and  comparing 
the  ratios  derived  from  the  four  analyses  in  which  the  TiO2 
has  been  recorded  as  over  1  per  cent.  The  results  are  given 
on  page  316. 

In  these  four  cases  it  will  be  observed  that  the  calculations 
give  the  closest  approximation  to  the  normal  tourmaline  ratio 
when  the  titanium  is  regarded  as  Ti2O3.  Moreover  when  the 
titanium  is  regarded  as  TiO2  the  departure  from  the  normal 
ratio  is  so  great  that  it  does  not  seem  probable  that  this  is  due 
wholly  to  defects  in  the  analyses.  Some  very  careful  and 

*  69,  70,  71,  and  72  quoted  in  Dana's  Mineralogy ;  73,  Bull.  U.  S.  Geolog. 
Survey,  No.  90,  p.  39;  74,  Zeitschr.  deutsch.  Geol.  Gesell.,  xxxix,  p.  238; 
75,  Min.  u.  Petr.  Mitth.,  ix,  p.  410 ;  76,  Zeitschr.  Kryst,  xx,  p.  93 ;  77  Min. 
Mag.,  xi,  p.  61. 


316  THE   CHEMICAL   COMPOSITION 

Total 
No.  Locality.  Premises.  SiO2     B2O3  hydrogen. 

f  Ti02,  1.61  per  cent  .  .  4  :  0.88  :  18.9 

51.  Monroe,  Conn.,  J  Neglecting  titanium  .  4  :  0.91  :  19.6 

ElSSs  (  Ti20s  1.45  per  cent  .  .  4  :  0.91  :  19.97 

(  Ti02  1.19  per  cent  .  .  4  :  0.95  :  18.5 
53.  Gouverneur,  K  Y.,  J  Keglecting  titanium  .  4  .  0.97  :  18.9 

Kl^s  (  Ti203  1.07  per  cent  .  .  4  :  0.97  :  19.2 

(  Ti02  1.10  per  cent    .  .  4  :  0.93  :  19.1 

56.  Snarum,  J  Neglecting  titanium.  .  4  :  0.96  :  19.7 

Jannasch  and  Kalb 


/  Ti02  1.22  per  cent    .  .  4  :  0.90  :  18.4 
59.  Tamatawe,  J  Neglecting  titauium    .  4  .  0.92  :  18.8 

(Ti203  1.10  per  cent  .  .  4:0.92:19.1 

exact   analytical  work  must  be  done,  however,  in  order  to 
decide  this  question  definitely. 

Constitution  of  tourmaline.  —  The  evidence  thus  far  presented 
may  be  considered  as  convincing  that  all  tourmalines  are 
derivatives  of  a  complex  borosilicic  acid  H20B2Si4O21,  and  it 
is  believed  that  further  analyses  will  not  alter  this  result, 
although  they  may  furnish  important  data  concerning  the 
constitution  of  the  acid.  All  of  the  hydrogen  atoms  of  this 
acid  in  tourmaline  are  not  replaced  by  metals,  for  the  different 
varieties  have  always  been  found  to  contain  water,  which 
indicates  the  presence  of  hydroxyl.  The  ratio  of  the  silica 
to  the  hydrogen  derived  from  water  (hydroxyl)  plus  the 
fluorine  is  not  constant,  but  varies  in  Riggs's  and  our  analyses 
from  4  :  3.14  (pale  green  tourmaline  from  Auburn,  Maine)  to 
4  :  2.48  (colorless  tourmaline  from  De  Kalb).  In  all  of  the 
analyses  in  which  water  has  been  estimated  directly,  a  suffi- 
cient quantity  has  been  obtained  to  yield  two  hydroxyls  in  the 
formula  ;  in  only  a  few  cases  has  the  amount  been  sufficient 
to  yield  three  hydroxyls.  We  are  thus  led  to  believe  in  the 
existence  of  two  hydroxyls  in  all  tourmalines,  and  it  seems 
natural  to  associate  them  with  the  two  boron  atoms.  The 
acid  consequently  becomes  H18(BOH)2Si4O19.  The  small 
amount  of  fluorine  which  is  found  in  many  varieties  of  tour- 
maline presumably  plays  the  same  role  as  hydroxyl,  or  is 


OF  TOURMALINE.  317 

isomorphous  with  it,  as  in  the  case  of  topaz,  of  chondrodite, 
and  of  other  minerals  containing  fluorine  and  hydroxyl.  The 
slight  excess  of  hydrogen  over  and  above  the  two  hydroxyls 
may  be  regarded  as  basic  hydrogen,  which  plays  the  r61e  of 
a  metal.  Such  a  relation  is  known  to  exist  in  complex  min- 
eral compounds.* 

One  of  the  peculiar  features  of  tourmaline  is  that  vary- 
ing proportions  of  metals  of  different  valences  and  of  essen- 
tially different  character  replace  the  hydrogens  of  the  acid 
H18(BOH)2Si4O19.  In  all  cases  thus  far  examined  aluminium 
predominates  and  is  present  in  sufficient  quantity  to  replace 
more  than  half  the  hydrogens.  From  this  it  has  been  inferred 
that  an  aluminium-borosilicic  acid  H9Al3(BOH)2Si4O19  is  char- 
acteristic for  all  varieties  of  tourmaline.  The  constitution  of 
this  acid  may  be  expressed  graphically  as  follows : 

/o- 

Al-O 

s°___^r==Si= 

Al-O— (B  .  OH)  —  O— (B  .  OH)  —  0-H 


It  would  seem  that  the  mass  effect  of  the  complex  radical 
[Al3(BOH)2Si4Oi9],  which  has  a  valence  of  nine,  is  suffi- 
ciently pronounced  to  control  or  dominate  all  types  of  tour- 
maline. Thus  it  apparently  makes  no  difference  whether  the 
nine  hydrogens  are  replaced  largely  by  aluminium  and  to  a 
slight  extent  by  alkalies ;  or  largely  by  magnesium  and  to  a 
slight  extent  by  aluminium  and  alkalies ;  or  to  about  an  equal 
extent  by  aluminium,  iron  or  magnesium  and  alkalies;  the 
result  in  all  cases  is  the  mineral  tourmaline,  with  its  character- 
istic crystallization  and  its  peculiar  optical  and  electrical 
properties. 

The  following  example  (compare  the  ratio  derived  from  the 

*  Amer.  Jour.  Sci.,  1890,  vol.  40,  p.  396. 


318  THE   CHEMICAL   COMPOSITION 

analysis  of  the  green  tourmaline  from  Haddam  Neck,  page 
310)  will  illustrate  the  method  of  determining  to  what  extent 
the  nine  hydrogens  of  the  tourmaline  acid,  H9Al3(BOH)2Si4O19, 
are  replaced  by  metals  of  different  valences  : 

Ratio.     Total  hydrogen 
equivalent,  or  20  H.          2(OH,F).     18  H.  3  Al.         9  H. 

A1208  2.327  2.327    1.385  0.942  ~  0.154  =  6.1  K'" 

FeO       0.059  \ 

5£S     S  \  °-169  °-169  0.169-^0.154=1.1  R" 

CaO       0.046 ) 

Na20 


Li2Q       A-nAfw.*."  0.178  0.178  -v-  0.154  =  1.2  R,' 

F  2°       0  060  \  0'404  0'308  °'096  0'096  •*•  °'154  =  °'6  H' 


20)3.078         2)2.770  9)1.385  9.0 

0.154  1.385  0.154 

From  the  ratio  of  the  total  hydrogen  equivalent,  ^  (repre- 
senting two  hydroxyls)  are  deducted.  The  remainder,  18  H, 
is  divided  by  two,  thus  determining  the  ratio  of  the  nine  H's 
replaced  by  A13  in  the  formula.  The  excess  of  the  aluminium 
or  trivalent  metal  ratio,  R'r/,  together  with  the  ratios  of  the 
bivalent  metals,  R",  the  alkali  metals  R'  and  the  excess  of 
hydrogen,  H,  represent  nine  H's,  which  are  divided  among  the 
different  constituents.  Thus  in  the  green  tourmaline  from 
Haddam  Neck  6.1  hydrogens  are  replaced  by  Al  (R'")>  1-1  by 
R",  1.2  by  R'  and  there  remains  0.6  excess  of  basic  hydrogen. 

The  analyses  of  Riggs,  Jannasch  and  Kalb,  Scharizer  and 
Chatard,  given  on  page  555  of  Dana's  Mineralogy,  together 
with  our  own  analyses,  practically  include  all  varieties  of  tour- 
maline which  have  thus  far  been  investigated,  and  in  the  fol- 
lowing table  are  given  the  results  of  applying  the  foregoing 
method  of  calculation  to  them : 

It  will  be  observed  that  the  extent  to  which  the  nine  hydro- 
gens of  the  acid  H9Al2(BOH)2Si4O19  are  replaced  by  metals,  is 
very  variable.  The  trivalent  metal,  R'",  is  chiefly  aluminium, 
and  the  extent  to  which  the  hydrogens  are  replaced  by  it 


OF  TOURMALINE. 


319 


Ibjj^  Magnesia  Magnesia-Iron  Iron  Tourmalines, 
?  Q  Tourraal.  Tourmalines.  No.  21  excepted.  Lithia  Tourmalines. 

No. 

Locality. 

Color. 

Analyst. 

E'" 

R" 

E' 

H 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 

35 

Minas  Geraes,  Brazil  .  . 
Rumford,  Me  
Brazil 

Pale  pink   . 
Rose   .  .  .  . 
Green  .... 
Colorless  .  . 
Pale  green  . 
Red  

Riggs,  37   .  .  .  . 
Riggs,  36 
Jann.  &  Kalb,  64 
Riggs,  38   .  .  .  . 
Riggs,  39   .  .  .  . 
Scharizer,  67  .  . 
Authors  

6.7 
6.5 
6.3 
6.2 
6.2 
6.1 
6.1 
6.0 
6.0 
5.9 
5.7 
5.5 
5.3 
4.7 
4.7 
4.7 
4.7 
4.7 
4.5 
4.4 
4.4 
4.3 
4.2 
4.0 
3.8 
3.7 
3.7 
3.6 
3.4 
3.1 
2.5 
2.2 
2.2 
2.0 

1.6 

0.3 
0.2 
1.1 
0.6 
0.8 
0.3 
1.1 
1.1 
1.3 
1.1 
0.9 
1.2 
1.5 
2.9 
3.0 
3.1 
3.2 
3.2 
3.0 
3.2 
3.4 
3.5 
3.6 
4.1 
4.6 
4.0 
4.4 
4.1 
4.1 
4.7 
5.7 
5.7 
5.6 
6.2 

6.3 

1.2 
1.2 
0.9 
1.1 
1.3 
1.3 
1.2 
1.4 
1.1 
1.3 
1.2 
1.2 
1.1 
0.7 
0.5 
0.5 
0.5 
0.7 
0.5 
0.6 
0.5 
0.5 
0.5 
0.5 
0.5 
0.5 
0.7 
0.6 
0.7 
0.5 
0.3 
0.4 
0.4 
0.2 

0.4 

0.8 
1.1 
0.7 
1.1 
0.7 
1.3 
0.6 
0.5 
0.6 
0.7 
1.2 
1.1 
1.1 
0.7 
0.8 
0.7 
0.6 
0.4 
1.0 
0.8 
0.7 
0.7 
0.7 
0.4 
0.1 
0.8 
0.2 
0.7 
0-8 
0.7 
0.5 
0.7 
08 
0.6 

0.7 

Auburn,  Me  
Minas  Geraes,  Brazil  .  . 
Schiittenhofen,  Bohemia 
Haddam  Neck,  Conn.  .  . 
Barra  do  Perahy,  Brazil 
Rumford  Me  

Pale  green  . 
Green.  .  .  . 
Dark  green 
Olive  green 
Light  green 
Blue  green  . 
Dark  green 
Black.  .  .  . 
Black.  .  .  . 
Black  .... 
Black  .... 
Black.  .  .  . 
Blue-black  . 
Black.  .  .  . 
Green  (Cr)  . 
Black.  .  .  . 
Black.  .  .  . 
Black.  .  .  . 
Black  .... 
Black.  .  .  . 
Black.  .  .  . 
Dark  brown 
Dark  brown 
Black.  .  .  . 
Colorless.  . 
Colorless  .  . 
Brown   .  .  . 
Brown   .  .  . 

Black.  .  .  . 

Jann.  &  Kalb,  63 
Riggs,  42 
Riggs,  41   .... 
Riggs,  40  .... 
Scharizer,  66  .  . 
Riggs,  43 
Jann.  &  Kalb,  62 
Riggs,  44   .  .  .  . 
Riggs,  45  .... 
Jann.  &  Kalb,  57 
Jann.  &  Kalb,  60 
Scharizer,  65  .  . 
Jann.  &  Kalb,  58 
Chatard,  72  ... 
Riggs,  46 
Riggs,  48   .... 
Jann.  &  Kalb,  61 
Jann.  &  Kalb,  59 
Riggs,  47 
Jann.  &  Kalb,  56 
Riggs,  52   .... 
Riggs,  51   .... 
Riggs,  49   .... 
Authors  . 

Minas  Geraes,  Brazil.  .  . 
Auburn  Me  .  .  .  . 

Schiittenhofen,  Bohemia 
Auburn,  Me  

Buckworth,  Australia  .  . 
Paris,  Me  
Auburn,  Me.  .  

Alabashka,  Russia  .... 
Mursinka  Russia.  . 

Schiittenhofen,  Bohemia 
Piedra  Blanca  

Montgomery  Co.,  Md.  . 
Minas  Geraes,  Brazil  .  . 
Stony  Point,  N.  C.  .  .  ..  . 
Olahpian.  

Tamatawe  
rladdam,  Conn  
Snarum,  Norway  
Orford  N.  H.  .  .  . 

Monroe,  Conn  
Nantic  Gulf,  Baffin's  Ld. 
DeKalb,  N.  Y  

DeKalb  NY  ...  . 

Riggs,  54  .... 
Riggs,  53  .... 
Riggs,  55   .... 

Riggs,  50  .  .  .  . 

Gouverneur  N.  Y 

Hamburg,  N.  J  

?ierrepont,  N.  Y  

ranges  from  6.7  to  1.6.  The  bivalent  metals  represented  by 
R"  are  chiefly  iron  and  magnesium,  and  the  extent  to  which 
the  hydrogens  are  replaced  by  them  ranges  from  0.3  to  6.3. 
In  general  R"  and  R;//  are  reciprocal.  There  is  always  some 
hydrogen  replaced  by  the  alkali  metals  R',  and  some  basic 
hydrogen.  The  results  are  arranged  in  the  table  according  to 
a  decrease  in  the  replacement  of  the  hydrogens  by  R//;,  and 
according  to  this  arrangement  the  different  varieties  of  tour- 
maline fall  into  natural  groups. 

The  first  13  examples  are  characterized  by  containing  an 
appreciable  quantity  of  lithium,  while  in  the  others  none,  or 


320  THE   CHEMICAL   COMPOSITION 

not  more  than  traces  of  this  element  have  been  found ;  these 
may  therefore  be  designated  as  Lithia  Tourmalines,  which  form 
a  natural  group.  In  this  group  R'  is  higher  than  in  other 
varieties,  while  H  is  somewhat  higher  than  the  general  aver- 
age; R//r  is  very  high  and  R"  correspondingly  low.  This 
variety  of  tourmaline  has  its  particular  mode  of  occurrence, 
being  found  in  pegmatite  veins  associated  with  quartz,  albite, 
microcline,  orthoclase,  muscovite  and  lepidolite.  The  material 
is  generally  delicately  colored  and  often  transparent  and  of 
gem-like  quality.  It  is  difficultly  fusible  when  heated  before 
the  blowpipe,  fusibility  =  5  -  5 J. 

At  the  opposite  extreme,  31-34,  are  varieties  which  may 
be  designated  as  Magnesia  Tourmalines.  In  these  R",  which 
is  chiefly  magnesium,  is  very  high  and  R'"  correspondingly 
low,  while  R'  reaches  its  lowest  limit,  0.2  to  0.4.  These 
varieties  are  light-colored  and  at  times  of  gem-like  quality. 
They  are  easily  fusible  before  the  blowpipe,  fusibility  =  3. 
With  these  No.  35  should  be  associated,  for  it  differs  only  in 
containing  considerable  iron  which  is  isomorphous  with  the 
magnesium,  hence  the  color  of  this  tourmaline  is  black. 
The  last  five  are  alike  in  their  mode  of  occurrence.  They 
have  probably  been  formed  in  limestones  containing  magne- 
sium by  the  contact  action  of  intruded  igneous  masses  during 
the  pneumatolitic  period,  when  such  masses  were  giving  off 
heated  aqueous  vapors  containing  boracic  acid  and  fluorine 
compounds.  They  are  found  in  coarse  crystalline  limestone, 
associated  with  graphite,  phlogopite,  pyroxene,  amphibole, 
scapolite  and  apatite.  Contact  metamorphisms  of  this  nature 
have  recently  been  described  by  Lacroix.* 

The  intermediate  varieties  (Nos.  14  to  30)  with  the  excep- 
tion of  No.  21  are  black  or  dark  brown,  owing  to  the  presence 
of  iron.  These  are  the  ordinary  tourmalines  found  in  granites, 
gneisses  and  schists,  and  sometimes  in  pegmatite  veins  inti- 
mately associated  with  lithia  tourmaline,  as  at  Auburn  and 
Paris,  Maine.  They  too  have  probably  resulted  from  the 

*  Les  Granites  des  Pyrenees  et  ses  Phenomenes  de  Contact,  Bull.  Carte 
Geologique  de  France,  No.  64,  Tome  x,  p.  54,  1898. 


OF   TOURMALINE.  321 

mineralizing  action  of  heated  aqueous  vapors  containing 
boracic  acid  and  fluorine  compounds,  given  off  during  the 
pneumatolitic  period  of  cooling  igneous  rocks.  A  contact 
metamorphism  of  this  character,  attended  by  the  formation 
of  tourmaline  vein  stone,  has  been  very  carefully  described 
by  Hawes.* 

Nos.  14  to  22  (No.  21  excepted)  are  characterized  by  con- 
taining iron  and  only  a  little  magnesia,  hence  they  may  be 
designated  as  Iron  Tourmalines ;  Nos.  23  to  30  contain  both 
magnesia  and  iron,  and  are  hence  designated  as  Magnesia-Iron 
Tourmalines.  These  two  groups,  however,  grade  into  one 
another.  The  fusibility  of  these  intermediate  groups  of  tour- 
malines varies  from  4.5  to  3,  and  decreases  as  the  amount  of 
iron  and  magnesia  increase. 

Although  in  this  series  of  thirty-five  analyses  there  are 
pronounced  groups  or  types  of  tourmaline  which  may  be 
recognized,  nowhere  in  the  series  do  the  ratios  of  R'",  R", 
R'  and  H  approximate  so  closely  to  rational  numbers  that  a 
definite  formula  for  any  one  type  can  be  instituted.  Riggs 
and  Jannasch  and  Kalb,  however,  have  given  special  formulas 
for  different  types  of  tourmaline  (pages  301  and  303)  based 
upon  multiples  of  the  acid  H18(BOH)2Si4Oi9.  Deducting 
from  their  formulas  appropriate  multiples  of  the  aluminium- 
borosilicic  radical  [Al3(BOH)2Si4Oi9],  it  is  found  that  the 
nine  variable  hydrogens  of  the  tourmaline  acid  are  replaced 
by  metals  of  different  valences  in  the  following  proportions  : 

R'"        R"         R'         H 

(Riggs  7.0    0.0    1.3    0.7 

I.    Lithia  tourmaline         •<  T  i-nr-n      />  n     i  *     10     no 

( Jann.  and  Kalb     6.0     1.4     1.3     0.3 

f  Riggs  5.0     2.6     0.7     0.7 

II.   Iron  tourmaline  1T  JTTI^     -n     on     AT     A  Q 

( Jann.  and  Kalb     o.O     3.0     0.7     0.3 

III.   Iron-magnesia  tour.         Jann.  and  Kalb     4.0     4.0     0.7     0.3 

Concerning  the  formulas  for  lithia  tourmaline,  Riggs's  cor- 
responds closely  to  No.  1,  and  Jannasch  and  Kalb's  to  Nos.  7, 

*  The  Albany  Granite,  New  Hampshire,  and  its  Contact  Phenomena,  see 
page  400. 

21 


322  THE   CHEMICAL   COMPOSITION 

8,  9,  and  10  of  our  series  (compare  the  table  on  p.  319),  but 
neither  of  these  complicated  formulas  furnishes  a  satisfactory 
expression  for  this  type  as  a  whole.  Similar  statements  might 
be  made  concerning  their  formulas  for  iron  tourmalines  and 
for  iron  magnesia  tourmalines.  The  endeavor  to  express  the 
composition  of  tourmaline  or  of  one  of  its  types  by  a  definite 
formula  may  be  compared  to  the  attempt  to  express  the  com- 
position of  the  dark  varieties  of  sphalerite  by  a  formula. 
Thus  ZnnFe4S16  would  correspond  to  sphalerite  containing 
about  50.5  per  cent  of  zinc  and  15.7  per  cent  of  iron,  but 
zinc  and  iron  are  isomorphous  and  can  mutually  replace  one 
another  in  sphalerite,  and  a  variety  containing  less  iron  would 
have  to  be  expressed  by  a  different  formula.  When,  however, 
we  understand  the  isomorphous  relations  existing  between 
zinc  and  iron,  and  express  the  composition  by  RS,  where  R 
=  Zn  and  Fe,  the  composition  becomes  very  much  simplified. 

In  tourmaline  we  have  an  isomorphous  relation  of  a  very 
peculiar  nature,  for  in  the  acid  H9Al3(BOH)2Si4O19  the  nine 
hydrogens  may  be  replaced  to  a  large  extent  either  by  the 
trivalent  metal  aluminium  or  by  the  bivalent  metals  magne- 
sium and  iron  without  any  decided  change  in  crystalline  form. 
This  leads  to  the  consideration  of  a  certain  phase  of  isomor- 
phism which,  as  it  seems  to  us,  has  not  been  considered  with 
sufficient  care,  namely,  the  mass  effect  of  complex  radicals  in 
influencing  or  controlling  crystallization.  Thus  in  their 
simple  salts  we  do  not  regard  sodium  and  potassium  as  iso- 
morphous with  calcium,  but  in  some  complex  silicates,  zeolites 
for  example,  we  recognize  Na2  and  K2  as  isomorphous  with, 
or  at  least  capable  of  replacing,  calcium,  barium,  and  strontium. 
In  some  of  the  phosphates,  dickinsonite  and  fillowite  for 
example,  we  have  sodium  (Na2)  playing  the  same  role  as 
calcium,  manganese,  and  iron  in  replacing  the  hydrogens  of 
phosphoric  acid.  In  the  garnet-sodalite  group  we  have  min- 
erals with  isometric  crystallization,  to  which  the  following 
formulas  have  been  assigned :  * 

*  Brogger  and  Backstrom,  Zeitschr.  fur.  Kryst.,  xriii,  p.  209,  1890. 


OF  TOURMALINE.  323 

Ca3Al2(Si04)3  Grossularite  > 

Fe3Al2(Si04)3  Almandite     j 

(Cl— Al)Na4Al2(Si04)3  Sodalite 

(NaS04— Al)Na4Al2(Si04)8  Noselite 

(NaS04— Al)  (Na2,  Ca)2Al2(Si04)3  Haiiynite 

(NaS3— Al)Na4Al2(Si04)3  Lazurite 

[(OH,  F,  Cl)2Al]6Al2(Si04)3  Zunyite 

When  it  is  taken  into  consideration  that  isometric  crystalliza- 
tion is  exceptional  in  the  group  of  silicates,  we  are  led  to 
believe  that  the  sexivalent  radical  [Al2(SiO4)3],  by  virtue  of 
its  mass  effect,  controls  or  dominates  the  crystallization  of 
these  minerals.  Not  only  are  they  isometric,  but,  with  the 
exception  of  zunyite,  which  is  tetrahedral,  they  all  crystallize 
commonly  in  dodecahedrons.  In  sodalite,  noselite,  and  lazurite, 
such  unlike  constituents  as  chlorine,  and  the  univalent  sul- 
phate and  polysulphide  radicals  (NaSO4)'  and  (NaS3)'  play 
the  same  part  in  the  complex  molecules.  It  is,  moreover,  prob- 
able that  these  unlike  constituents  are  isomorphous  in  the  sense 
that  they  can  mutually  replace  one  another,  for  Brogger  and 
Backstrom  have  described  homogeneous  material  containing 
the  lazurite,  haiiynite  and  sodalite  molecules,  while  appreci- 
able quantities  of  chlorine  are  almost  always  found  in  noselite 
and  haiiynite,  thus  indicating  the  presence  of  the  isomorphous 
sodalite  molecule.  It  is  to  be  expected  that  the  larger  and 
more  complex  the  radical  the  more  potent  will  be  its  mass  effect 
in  controlling  or  determining  the  crystal  form.  Thus  in 
sodalite,  noselite  and  haiiynite  the  radical  is  very  large, 
[R'4Al2(SiO4)3],  R'4  =  Na4  or  Ca2. 

Tourmaline,  it  would  seem,  furnishes  an  example  somewhat 
analogous  to  that  presented  by  the  garnet-sodalite  group.  In 
the  acid  H9Al3(BOH)2Si4Oi9  the  mass  effect  of  the  complex 
radical  [Al3(BOH)2Si4Oi9]  is  so  great,  or,  the  r61e  played  by 
the  replacement  of  the  nine  hydrogens  is  so  subordinate,  that 
the  bivalent  elements,  Fe,  Mg,  Mn,  and  Ca,  and  to  a  slight 
extent  the  alkalies,  Li,  Na,  and  K,  can  replace  aluminium  as 
isomorphous  constituents.  This  conclusion  in  some  respects 
is  analogous  to  that  reached  by  Rammelsberg,  who  stated  in 


324       CHEMICAL    COMPOSITION  OF   TOURMALINE. 

1870  that  all  tourmalines  were  derived  from  an  acid  H6SiO5,  in 
which  the  six  hydrogens  were  replaced  in  varying  proportions 
by  R'6,  R"3,A12  and  B2.  Applying  Rammelsberg's  idea  to  the 
acid  H18(BOH)2Si4O19,  all  varieties  of  tourmalines  may  be 
regarded  as  mixtures  of  the  molecules 

R'18(BOH)2Si4O19,  R'    =  Li,  Na,  K,  and  H 

R"9(BOH)2Si4O19,  R"  =  Fe>  Mg>  Mn>  and  Ca 
R'"6(BOH)2Si4Oi9,  R'"  =  Al,  Cr,  and  small  amounts  of  Fe  and  Ti. 

It  seems  more  logical  and  satisfactory,  however,  to  consider 
all  varieties  of  tourmalines  as  salts  of  the  acid  H9A18(BOH)2 
Si4Oi9,  in  which  the  complex  aluminium-borosilicic  acid  radical 
[Al3(BOH)2Si4Oi9]  exerts  a  mass  effect  by  virtue  of  which  the 
remaining  hydrogens  may  be  replaced  by  metals  of  essentially 
different  character  without  bringing  about  any  pronounced 
change  in  crystalline  form. 


SOME   NEW   MINERALS   FROM 

THE  ZINC  MINES  AT  FRANKLIN,  N.  J,  AND  NOTE 
CONCERNING  THE  CHEMICAL  COMPO- 
SITION   OF   GANOMALITE. 

BY  S.   L.  PENFIELD  AND  C.   H.   WARREN. 
(From  Amer.  Jour.  Sci.,  1899,  vol.  8,  pp.  339-353.) 

THE  minerals  to  be  described  in  the  present  paper  came  for 
the  most  part  from  the  one-thousand-foot  level  of  the  Parker 
Shaft  on  North  Mine  Hill.  Unfortunately  at  the  time  that 
they  were  brought  to  the  surface,  about  two  years  ago,  the  fact 
that  several  new  species  were  being  mined  was  not  known,  and 
a  quantity  of  material,  which  it  is  believed  would  prove  to  be 
very  profitable  hunting-ground  for  the  new  species  was  thrown 
upon  the  dump  and  subsequently  covered  up.  Our  attention 
has  been  called  to  these  minerals  at  different  times  by  Messrs. 
E.  P.  Hancock,  of  Burlington,  N.  J.,  J.  J.  McGovern,  of 
Franklin,  F.  L.  Nason,  of  West  Haven,  Conn.,  F.  A.  Canfielcl, 
of  Dover,  N.  J.,  and  W.  M.  Foote,  of  Philadelphia,  Pa.,  while 
both  of  the  writers  at  separate  visits  to  the  locality  have  been 
able  to  collect  a  few  specimens.  The  new  species  were  found 
in  a  somewhat  limited  area,  and  it  is  especially  interesting  to 
note  the  minerals  which  are  associated  with  them,  for  they  are 
very  unusual  even  for  Franklin,  N.  J.,  and  would  seem  to 
indicate  that  peculiar  conditions  prevailed  during  the  period 
when  these  minerals  were  being  formed.  The  associated  min- 
erals are  as  follows  :  Native  lead  *  and  copper,  f  clinohedrite, J 
roeblingite,§  axinite  in  transparent  yellow  crystals,  willemite 

*  Amer.  Jour.  Sci.,  1898,  vol.  4,  p.  187. 

t  Proc.  Am.  Acad.  of  Arts  and  Sci.,  xxxiii,  p.  429,  1898. 

J  This  volume,  p.  291. 

§  Am.  Jour.  Sci.,  1897,  vol.  3,  p.  413. 


326  SOME  NEW  MINERALS 

in  exceptionally  fine,  transparent  green  crystals,  vesuvianite, 
datolite,  barite,  garnet,  brownish-black  phlogopite,  and  a  little 
franklinite.  The  presence  of  axinite  and  datolite  containing 
boron  and  of  phlogopite  would  seem  to  indicate  that  the  min- 
erals, part  of  them  at  least,  have  resulted  from  metamorphism 
brought  about  by  the  action  of  intruded  igneous  masses  either 
during  the  pneumatolitie  period  when  such  masses  were  giv- 
ing off  heated  aqueous  vapors  carrying  boron  and  fluorine 
compounds,  or  during  a  period  when  heated  waters,  laden 
with  mineralizing  agents,  were  circulating  through  the  deposit. 

1.  HANCOCKITE. 

This  mineral  was  found  in  considerable  quantity  both  mas- 
sive and  in  cellular  masses  of  a  brownish-red  or  maroon  color, 
and  attention  has  already  been  called  to  it  as  a  new  species  by 
Penfield  and  Foote  in  their  description  of  clinohedrite.  Thus 
far  it  has  been  observed  only  in  very  small,  lath-shaped  crys- 
tals, the  largest  being  not  over  0.5  mm.  in  length  and  0.15  mm. 
in  diameter,  and  these  generally  are  so  intimately  associated 
with  garnet,  axinite,  and  phlogopite  that  it  was  for  a  long  time 
difficult  to  secure  a  specimen  from  which  a  sufficient  quantity 
of  the  pure  material  could  be  obtained  for  the  chemical  analysis. 


FIGURE  1. 

The  accompanying  figure  is  a  sketch  of  one  of  the  crystals  as 
seen  under  the  microscope.  The  faces  are  striated  parallel  to 
the  longer  axis  of  the  crystals,  and  they  round  into  one  another 
owing  to  oscillatory  combinations.  The  terminal  faces,  neces- 
sarily very  small,  are  .vicinal,  and  it  has  thus  far  been  impossi- 
ble to  find  any  crystal  from  which  satisfactory  measurements 
of  the  interfacial  angles  could  be  obtained.  As  may  be  seen 
from  the  figure  the  habit  of  the  crystals  is  like  that  of  epidote ; 
that  is,  the  prominent  faces  are  parallel  to  the  axis  of  symme- 


FROM  FRANKLIN,  N.  J.  327 

try,  and  the  crystals  are  terminated  by  two  faces  correspond- 
ing to  the  form  ?i(lll)  of  epidote.  On  one  of  the  crystals  it 
was  possible  to  obtain  approximate  measurements  with  the 
Fuess  reflecting  goniometer  by  using  a  strong  illumination 
of  the  signal  and  the  8  ocular.  The  measurements,  given  in 
the  accompanying  table,  although  not  sufficiently  accurate  for 
establishing  an  axial  ratio,  indicate  that  the  forms  and  angles 
of  hancockite  are  similar  to  those  of  epidote. 

Hancockite, 
Approximate  measurements.  Epidote. 

c  A  e,  001  A  101  =  36°  15'  34°  43' 

e  A  a,  101  A  100  =  30°  45'  29°  54' 

c  A  r,  001  A  T01  =  63°  63°  42' 

r  A  a,  T01  A  TOO  =  55°  3(X  51°  41' 

WAW,  T11A11T=  67°  70°  29' 

CAW,  001  A  Til  =  77°  75°  11' 

Although  the  appearance  of  the  mineral  in  the  hand  speci- 
men varies  from  a  dark  to  a  light  brownish-red,  single  crystals, 
as  seen  with  a  pocket  lens,  have  a  yellowish-brown  color.  Crys- 
tals like  Figure  1,  when  examined  with  the  polarizing  micro- 
scope, exhibit  distinct  pelochroism,  yellowish-brown  for 
vibrations  parallel  to  b,  which  corresponds  to  the  crystallo- 
graphic  axis  6,  and  somewhat  variable  for  vibrations  at  right 
angles  to  this  direction,  being  delicate  rose  color  at  the  attached 
end  and  grading  to  pale,  somewhat  greenish-yellow  at  the  ter- 
minated end.  On  some  very  small  individuals  the  delicate  rose 
color  was  observed  throughout  the  whole  length  of  the  crys- 
tals. With  crossed  nicols  the  crystals  show  an  extinction 
when  their  longer  or  symmetry  axis  is  parallel  to  the  plane  of 
the  polarizer.  In  convergent  light  something  of  the  outer 
rings  of  the  biaxial  interference  figure  could  be  seen,  accom- 
panied by  a  dark  bar,  indicating  plainly  that  the  optical  axes 
are  in  the  symmetry  plane.  By  rotating  a  crystal,  when 
immersed  in  the  potassium  mercuric-iodide  solution,  the  optical 
axes  could  be  brought  separately  to  the  center  of  the  field  and 
their  divergence  2  V  was  found  to  be  approximately  50°. 

The  luster  of  the  hancockite  crystals  is  vitreous,  and  the 


328  SOME  NEW  MINERALS 

hardness  is  about  6.5-7.  Owing  to  the  small  size  of  the  crys- 
tals and  their  intimate  association  with  garnet,  axinite  and 
willemite,  considerable  difficulty  was  experienced  in  finding  a 
specimen  from  which  a  sufficient  quantity  of  pure  material 
could  be  obtained  for  analysis.  A  specimen,  however,  finally 
came  to  us  through  Mr.  Hancock,  consisting  of  a  cellular 
mass  in  which  the  walls  and  the  drusy  lining  consisted  chiefly 
of  hancockite.  By  crushing  this  specimen,  picking  out  the 
small  fragments  and  examining  them  with  a  lens,  it  was  pos- 
sible to  obtain  the  mineral  almost  absolutely  free  from  the 
associated  garnet  and  axinite,  which  could  be  distinguished  by 
their  lighter  color.  An  attempt  to  separate  the  minerals  by 
differences  in  their  specific  gravity  was  not  successful.  The 
specific  gravity  of  the  carefully  selected  material  was  found  to 
be  4.030. 

Concerning  the  method  of  analysis,  the  only  points  which 
need  to  be  specially  commented  upon  are  the  following :  After 
separation  of  the  silica,  the  lead  was  precipitated  with  hydro- 
gen sulphide  and  subsequently  converted  into  sulphate  and 
weighed.  The  iron  and  alumina  were  separated  from  the 
bivalent  metals  by  a  basic  acetate  precipitation,  reprecipitated 
b}r  ammonia  and  weighed  as  oxides,  the  iron  being  estimated 
subsequently  by  means  of  potassium  permanganate.  The  cal- 
cium and  strontium  were  converted  into  nitrates  and  separated 
by  means  of  amyl  alcohol  as  directed  by  Browning.*  Water 
was  estimated  by  loss  on  ignition.  Careful  tests  failed  to 
reveal  the  presence  of  any  ferrous  iron.  The  deep  color  of 
the  crystals  at  first  suggested  the  idea  that  the  mineral  would 
be  rich  in  manganese,  which  is  by  no  means  the  case.  The 
color,  however,  is  probably  due  to  the  presence  of  some  higher 
oxide  of  manganese  which  is  known  to  impart  an  intense  color 
to  silicates  and  was  estimated  by  the  method  described  by 
Penfield.f 

The  results  of  the  analysis  by  Warren  are  as  follows :  — 

*  Amer.  Jour.  Sci.,  1892,  vol.  43,  p.  50. 
t  Ibid.,  1893,  vol.  46,  p.  291. 


FROM  FRANKLIN,  N.  J. 


329 


Partial 


Si02 

A1203 

Fe208 

Mn203 

PbO 

MnO 

MgO 

CaO 

SrO 

H20 


30.99 

17.89 

12.30 

1.38 

18.47 

2.12 

0.52 

11.50 

3.89 

1.62 


Average. 

Ratio. 

Analysis. 

.   .  . 

30.99 

0.516                 SiO2 

6.00 

SiO2 

30.88 

17.89 

0.173  \ 

A1203 

17.99 

12.37 

12.33 

0.077  [  0.259    R2O3 

3.00 

Fe203 

12.96 

.  .  . 

1.38 

0.009  ) 

.  .  . 

18.59 

18.53 

0.083 

PbO 

17.47 

2.12 

0.029 

MnO 

2.96 

.  .  . 

0.52 

0.013 

0.367    RO 

4.26 

MgO 

1.02 

11.50 

0.205 

CaO    \ 

15.33 

.  .  . 

3.89 

O.Q37 

SrO    ! 

.  .  . 

1.62 

0.090                 H2O 

1.06 

1.62 

100.77 


100.23 


The  ratio  of  SiO2 :  R2O3  :  RO  :  H2O  approximates  closely  to 
6:3:4:1,  which  gives  as  the  empirical  formula  H2R"4R"/6 
SieO^,  or  R"2(R"'OH)R"'2(SiO4)3.  The  general  formula  is 
that  of  epidote,  but  the  material  differs  from  any  variety  of 
that  mineral  previously  described  in  having  the  bivalent 
metals  lead  and  strontium  isomorphous  with  calcium.  Owing 
to  its  color  and  the  presence  of  manganese  sesquioxide  the 
mineral  is  allied  to  piedmontite.  It  will  be  observed  that  the 
quantity  of  protoxide,  RO,  indicated  by  the  analysis,  is  a  trifle 
high,  SiO2 :  RO  being  6  :  4.26  instead  of  6  :  4,  as  it  should 
be  to  satisfy  the  epidote  formula.  The  analyses,  however, 
were  made  with  very  great  care,  and  in  the  determination  of 
the  calcium  and  strontium  the  separated  oxides  were  converted 
into  sulphates  and  thus  found  to  have  the  correct  molecular 
weight.  The  partial  analysis  given  was  made  on  material 
taken  from  the  same  specimen  as  used  for  the  other  analysis, 
but  the  higher  oxide  of  manganese  was  not  determined  and 
strontium  was  not  separated  from  the  calcium. 

In  its  chemical  as  well  as  in  its  crystallographic  relations, 
hancockite  is  a  member  of  the  epidote  group  of  minerals,  and 
should  occupy  a  position  next  to  piedmontite  in  a  system  of 
mineralogy.  It  is  especially  interesting  on  account  of  the 
considerable  quantities  of  lead  and  strontium  which  it  con- 
tains, elements  thus  far  observed  in  combination  with  silicic 
acid  in  only  a  few  rare  mineral  species. 

Before  the  blowpipe,  hancockite  fuses  with  intumescence  at 


330 


SOME  NEW  MINERALS 


3  to  a  black,  slightly  magnetic  globule.  The  globule  becomes 
more  strongly  magnetic  if  heated  on  charcoal.  With  sodium 
carbonate  on  charcoal  a  coating  of  lead  oxide  is  obtained. 
Reacts  for  manganese  with  the  sodium  carbonate  bead  in  O  .  F. 
The  mineral  is  insoluble  in  hydrochloric  acid,  but,  like  epidote, 
after  fusion  it  dissolves  and  yields  gelatinous  silica  upon 
evaporation.  In  the  closed  tube,  at  a  high  temperature,  a 
little  water  is  given  off. 

A  considerable  quantity  of  hancockite  was  taken  from  the 
mine  at  one  time,  and  it  is  the  most  abundant  of  the  new 
species  described  in  this  paper.  It  is  named  after  Mr.  E.  P. 
Hancock  of  Burlington,  N.  J. 

2.   GLAUCOCHROITE. 

This  mineral  was  collected  by  S.  L.  Penfield  in  September, 
1898,  and  was  subsequently  sent  to  New  Haven  for  identifica- 
tion by  Mr.  W.  M.  Foote,  who  had  collected  several  specimens 
of  it  earlier  in  the  season.  It  occurs  in  prismatic  crystals 
belonging  to  the  orthorhombic  system,  and  in  columnar 
aggregates  imbedded  in  a  white  matrix.  The  largest  crystals 
thus  far  observed  do  not  average  over  2  mm.  in  greatest 
diameter,  while  the  length  of  some  of  the  columnar  aggregates 
somewhat  exceeds  10  mm. 

Isolated  crystals  generally  show  the 
form  of  a  prism  w(110),  sometimes  in 
combination  with  a  second  prism  s(120), 
and  thus  far  all  attempts  to  find  a  crystal 
with  terminal  faces  have  proved  unsuc- 
cessful. A  few  penetration  and  contact 
twins  have  been  observed,  the  twinning 
plane  being  the  brachydome  (Oil),  and 
the  vertical  axes  of  the  individuals  cross- 
ing at  angles  of  about  60°  and  120°. 
Figure  2  is  an  illustration  of  one  of  these 
penetration  twins,  drawn  with  the  camera 
lucida  as  it  appeared  under  the  micro- 
scope. On  the  twin  crystals  the  pinacoid  a(100)  is  generally 


FIGURE  2. 


FROM  FRANKLIN,  N.  J.  331 

developed,  although  it  was  not  observed  on  any  of  the  simple 
crystals. 

The  prismatic  faces,  although  bright,  were  vicinal,  and  con- 
sequently it  was  difficult  to  obtain  reliable  measurements  of 
the  prismatic  angle.  The  average  of  a  number  of  measure- 
ments of  m  A  w,  110  A  lIO,  was  found  to  be  47°  32',  and  this 
angle,  taken  as  fundamental,  agreed  very  closely  with  the 
values  derived  from  the  best  reflections.  As  terminal  planes 
were  not  observed,  the  angle  between  the  vertical  axes  of  two 
prisms  in  twin  position  was  measured  under  the  microscope 
and  found  to  be  121°.  Assuming  the  twinning  plane  to  be  the 
brachydome  (Oil),  the  angle  of  Oil  A  Oil  was  thus  found  to 
be  59°,  which  was  taken  as  the  second  fundamental  angle. 
From  the  foregoing  fundamental  angles  the  axial  ratio  has  been 
calculated,  and  is  given  below,  together  with  the  axial  ratios 
of  monticellite  and  chrysolite,  to  which  species  glaucochroite 
is  closely  related,  it  being  a  manganese  monticellite. 

Glaucochroite,  a  :  b  :  c  =  0.440  :  1  :  0.566 
Monticellite,  a  :  b  :  c  =  0.431  :  1  :  0.576 
Chrysolite,  a  :  b  :  c  =  0.466  :  1  :  0.586 

No  reliable  reflections  could  be  obtained  from  the  second 
prism  s(120).  Approximate  measurements  are  120Al20  = 
99°,  calculated  97°  16' and  T/IAS,  110A120,  =17°  21',  calculated 
17°  36'.  A  rather  poor  basal  cleavage  was  detected,  and 
measurements  from  this  cleavage  on  to  the  prism  faces  gave 
angles  of  90°. 

The  hardness  is  about  6.  The  specific  gravity,  taken  with 
the  pycnometer  is  3.407.  The  fracture  is  conchoidal.  The 
luster  is  vitreous  and  the  color  is  a  delicate  bluish  green,  very 
similar  to  that  of  the  aquamarine  variety  of  beryl.  Minute 
crystals  are  almost  colorless,  and  on  a  few  of  the  specimens 
there  were  small  areas  where  the  mineral  exhibited  a  delicate 
pink  color. 

The  optical  orientation  is  a  =  b,  b  =  c  and  c  =  a-  The  plane  of 
the  optical  axes  is  the  base  (001)  and  the  acute  bisectrix  is 
normal  to  the  brachypinacoid  5(010).  The  double  refraction 


332  SOME  NEW  MINERALS 

is  therefore  negative.  Prismatic  crystals  served  as  prisms  for 
determining  the  indices  of  refraction  a  =  1.686  and  /3  =  1.722. 
These  values  were  each  derived  from  the  mean  of  four  inde- 
pendent measurements  which  showed  considerable  variation, 
owing  to  the  vicinal  character  of  the  prismatic  faces,  but  is 
believed  that  they  represent  a  close  approximation  to  the  true 
values.  On  a  section  parallel  to  the  pinacoid  (010),  which 
measured  0.5  x  1.5  mm.,  the  divergence  of  the  optical  axes  for 
yellow  light,  Na  flame,  was  measured  on  the  Fuess  axial  angle 
apparatus  as  follows :  2  E  =  121°  30'  and  2H  in  a-mono- 
bromnaphthalene  =  63°  27'.  From  these  values  2Vy  was  found 
to  be  60°  53'  and  60°  49',  respectively.  The  dispersion  was 
marked  p  >  v.  From  the  values  a,  /3  and  V,  y  was  calculated 
and  found  to  be  1.735.  The  optical  orientation,  dispersion,  and 
the  character  of  the  double  refraction  of  glaucochroite  are  like 
those  of  monticellite  as  determined  by  Penfield  and  Forbes.* 
The  indices  of  refraction  for  yellow  light  and  the  divergence 
of  the  optical  axes,  2V,  of  glaucochroite,  monticellite  and 
chrysolite  are  given  below  for  comparison : 

a  &  y  7  —  o  2  V  over  a 

Glaucochroite,     1.686  1.722  1.735  0.049  60°  61' 

Monticellite,        1.6505  1.6616  1.6679  0.0174  75°    2' 

Chrysolite,!         1.661  1.678  1.697  0.036  92°  14' 

Very  pure  material  for  the  chemical  analysis  was  obtained 
by  picking  out  the  small  prismatic  crystals  which  separated 
readily  from  the  matrix.  The  results  of  the  analysis  by 
Warren  are  as  follows : 

PQ.,.  Corrected  Theory  for 

Batlo>  analysis.  CaMnSi04. 


Si02 
MnO 
CaO 
PbO 
FeO 

31.48 
38.00 
28.95 
1.74 
trace 

0.524 
0.535 
0.517 

1.00 
1.02 
0.99 

31.98 
38.60 
29.42 
100.00 

32.08 
37.97 
29.95 

100.00 

100.17 

*  Amer.  Jour.  ScL,  1896,  vol.  50,  p.  135. 

t  DesCloizeaux,  Memoires  de  1'Institut  de  France,  T.  xviii,  p.  591. 


FROM  FRANKLIN,  N.  J.  333 

Leaving  out  of  consideration  the  small  amount  of  PbO, 
which,  owing  to  its  high  molecular  weight,  had  only  a  slight 
effect  upon  the  ratio,  the  ratio  of  SiO2 :  MnO  :  CaO  =  1.00  : 
1.02 :  0.99,  or  a  very  close  approximation  to  1:1:1.  The 
formula  of  glaucochroite  is  therefore  CaMnSiO4,  that  of  monti- 
cellite  being  CaMgSiO*.  With  the  above  analysis  we  have 
given  the  corrected  analysis,  after  disregarding  1.74  per  cent 
of  PbO  and  calculating  to  100  per  cent,  and  also  the  theoretical 
composition  corresponding  to  the  formula  CaMnSiO*.  Glau- 
cochroite takes  therefore  a  place  in  the  system  of  mineralogy 
next  to  monticellite  as  a  member  of  the  chrysolite  group. 

Glaucochroite  fuses  quietly  before  the  blowpipe  at  about 
3.5  to  a  brownish  black  globule,  and  imparts  no  color  to  the 
flame.  The  powdered  mineral  dissolves  easily  in  hydrochloric 
acid,  and  the  solution  yields  gelatinous  silica  upon  .evaporation. 
A  little  of  the  concentrated  solution,  when  brought  into  contact 
with  a  drop  of  sulphuric  acid  on  a  watch  glass,  gives  a  pre- 
cipitate of  calcium  sulphate.  With  either  the  borax  or  sodium 
carbonate  beads  a  strong  reaction  for  manganese  is  obtained. 

So  far  as  known,  only  a  small  amount  of  glaucochroite  has 
been  found.  Its  crystals  occur  imbedded  in  a  white  matrix, 
nasonite  (see  beyond),  and  intimately  associated  with  brown 
garnet  and  yellow  axinite.  The  name  glaucochroite  has  been 
given  to  this  species  because  of  its  color,  from  ryXav/cds  =  Hue- 
green  and  %/oota  =  color. 

3.   NASONITE. 

This  material  constitutes  the  matrix  in  which  the  crystals  of 
glaucochroite  are  generally  imbedded.  It  occurs  massive,  of 
white  color,  greasy  to  adamantine  luster,  hardness  about  4,  and 
hand  specimens  usually  present  a  mottled  or  spotted  appearance 
owing  to  numerous  inclusions  of  yellow  axinite  and  brown 
garnet,  which  are  scattered  rather  uniformly  through  the 
massive  nasonite.  The  material  that  has  been  examined 
consists  of  a  few  specimens  collected  by  S.  L.  Penfield  and 
some  sent  to  us  by  Mr.  W.  M.  Foote. 

Thin  sections  when  examined  with  the  polarizing  microscope 


334  SOME  NEW  MINERALS 

show  that  the  material  is  crystalline,  and  that  the  masses  con- 
sist of  an  intergrowth  of  crystal  particles,  some  of  which  are 
several  millimeters  in  diameter.  No  pronounced  cleavages 
were  observed  under  the  microscope,  and  no  crystal  boundaries 
were  detected  which  gave  any  clue  to  the  system  of  crystalli- 
zation. In  convergent  polarized  light,  however,  certain  sections 
gave  a  uniaxial  interference  figure,  and,  since  the  massive  min- 
eral broke  up  at  times  into  rude  rectangular  blocks,  it  may  be 
inferred  that  the  crystallization  is  tetragonal  and  that  the 
cleavage,  which  is  poor,  is  prismatic  and  basal.  The  bire- 
fringence is  rather  strong,  and  the  character  of  the  double 
refraction  is  positive. 

Material  for  the  chemical  analysis  was  obtained  by  crushing 
a  large  fragment  and  picking  out  the  purest  material  by  hand. 
The  specific  gravity  was  found  to  be  5.425.  The  results  of 
the  analysis  by  Warren  are  as  follows : 

Ratio. 

3.00 
0.516        5.03 

0.108        1.05 

-f-  y  =  u.UZiJ  ) 
100.17 

Oxygen  equivalent  of  Cl      0.63 

99.54 

The  ratio  of  SiOa:(Pb  +  Zn+Mn+Fe  +  Ca)O:(Cl+OH)  = 
3.00 :  5.03  :  1.05  which  approximates  closely  to  3  :  5  :  1,  and, 
since  two  chlorine  atoms  are  equivalent  to  one  oxygen,  this 
leads  to  the  general  formula  Ri0Cl2Si6O2i,  R  =  Pb  and  Ca,  and 
only  traces  of  Zn,  Mn,  and  Fe.  Before  discussing  the  general 
formula  further,  it  may  be  stated  that  there  were  observed, 
intimately  associated  with  the  nasonite,  a  few  particles  of 
clinohedrite,  H2CaZnSiO5,  and  it  is  probable  therefore  that  the 
small  percentage  of  zinc  (0.82  per  cent  ZnO)  was  derived  from 


i. 

n. 

Average. 

Ratio. 

Si02 

18.47 

18.47 

18.47 

0.308 

PbO 

65.84 

65.52 

65.68 

0.294" 

ZnO 

0.84 

0.80 

0.82 

0.010 

MnO 

0.90 

0.76 

0.83 

0.011 

FeO 

0.10 

... 

0.10 

0.001 

CaO 

11.20 

11.20 

11.20 

0.200. 

Cl 

2.80 

2.82 

2.81 

0.079  | 

H20 

0.27 

0.26 

0.26^ 

9  =  0.029  J 

FROM  FRANKLIN,  N.  J.  335 

a  slight  admixture  of  this  latter  mineral.  It  seems  therefore 
best  to  deduct  from  the  foregoing  analysis  the  ZnO,  and 
sufficient  amounts  of  SiO2,CaO  and  H2O  to  form  the  clinohe- 
drite  molecule.  The  ratio  then  becomes  SiO2 :  (Pb  +  Mn  +  Fe 
+  Ca)0  :  (Cl  +  OH)  -  0.298 :  0.496  :  0.098  =  3.00  :  5.01 :  0.99, 
or  almost  exactly  3:5:  1.  Furthermore  the  ratio  of  SiO2  : 
PbO  :  (Ca  +  Mn  +  Fe)O  :  (Cl  +  OH)  =  0.298  :  0.294  :  0.202  : 
0.098  =  3.00  :  2.97  :  2.04  :  0.99  or,  very  closely,  3:3:2:1. 
Since  Fe,  Mn,  and  water  (hydroxyl)  are  present  only  in  very 
small  amounts,  they  may  practically  be  disregarded,  and 
the  empirical  formula  expressed  as  Pb6Ca4Cl2(Si2O7)3,  or 
Pb4(PbCl)'2Ca4(Si207)3. 

Below  we  have  given  the  analysis,  after  deducting  2.16  per 
cent  of  clinohedrite,  substituting  for  MnO  and  FeO  equivalent 
amounts  of  CaO,  for  the  remaining  0.09  per  cent  of  water 
(hydroxyl)  an  equivalent  of  chlorine,  and  calculating  to  100 
per  cent.  For  comparison,  the  theoretical  composition  cor- 
responding to  the  formula  Pb6Ca4Cl2(Si2O7)3  is  also  given. 

Analysis  corrected.  Theory. 

Si02 18.32  18.21 

PbO 67.32  67.68 

CaO 11.59  11.33 

Cl 3.57  3.59 

100.80  100.81 

0  =  2C1.  .  .  .  0.80  0.81 

100.00  100.00 

Before  the  blowpipe,  nasonite  is  very  apt  to  decrepitate,  but 
if  a  fragment  can  be  held  in  the  forceps  it  fuses  at  about  2  to 
a  semi-transparent  globule,  and  the  characteristic  flame  colora- 
tion of  lead  is  obtained.  In  the  closed  tube  the  mineral  gives 
a  trace  of  water  and  an  abundant  sublimate  of  lead  chloride, 
the  residual  mineral  fusing  to  an  amethystine  glass  in  the  bottom 
of  the  tube.  The  powdered  mineral,  when  heated  alone  on 
charcoal  in  the  reducing  flame,  gives  a  white  sublimate  of  lead 
chloride  distant  from  the  assay,  a  yellow  coating  of  oxide  nearer, 
and  globules  of  metallic  lead.  The  mineral  is  readily  soluble 


336  SOME  NEW  MINERALS 

in  dilute  nitric  acid,  and  the  solution  yields  gelatinous  silica 
upon  evaporation. 

The  mineral  is  named  after  Mr.  Frank  L.  Nason  of  West 
Haven,  Connecticut,  formerly  of  the  Geological  Survey  of 
the  State  of  New  Jersey. 

Note  concerning  the  Chemical  Composition  of  GANOMALITE. 

Nasonite  is  closely  related  to  ganomalite,  to  which  the  em- 
pirical formula  Pb3Ca2Si3O11  has  been  assigned,  a  little  calcium 
being  replaced  by  manganese.  The  foregoing  formula,  when 
doubled,  may  be  written  as  a  slightly  basic  salt,  as  follows : 
Pb4(Pb2O)//Ca4(Si2O7)8,  which  is  like  the  formula  of  nasonite, 
except  that  the  bivalent  basic  lead  oxide  radical  (Pb2O)  of 
ganomalite  takes  the  place  of  the  two  univalent  lead  chloride 
radicals  (PbCl)  of  nasonite.  The  analogy  between  the  two 
minerals,  however,  becomes  still  closer  if  two  univalent  lead 
hydroxide  radicals  (PbOH)  are  substituted  for  the  bivalent 
basic  lead  oxide  radical  as  follows :  Pb4(PbOH)2Ca4(Si2O7)3, 
and  we  hope  to  be  able  to  show  that  this  is  undoubtedly  the 
correct  formula  for  ganomalite.  The  amount  of  water  neces- 
sary to  yield  two  hydroxyls  in  the  complex  ganomalite  mole- 
cule is  a  trifle  less  than  one  per  cent,  a  quantity  which  might 
have  been  easily  overlooked.  In  two  analyses  of  ganomalite 
from  Jakobsberg,  Sweden,  by  Wiborgh,  quoted  by  Sjogren,* 
neither  water  nor  loss  on  ignition  are  recorded,  while  in  an 
analysis  by  Lindstrom  f  a  loss  on  ignition  of  0.57  per  cent  is 
given,  and,  what  is  also  very  significant,  the  presence  of  a 
little  chlorine  is  recorded.  Lindstrom's  analysis  is  as  follows  : 

Analysis  Theory  for 

Analysis.  Ratio.  recalculated.  Pb4(PbOH)2Ca4(Si207)3. 

Si02  18.33  0.306  3.00    Si02  18.51  18.56 

PbO  68.80  0.308  3.02    PbO  69.46  68.97 

MnO  2.29  0.032}  CaO  11.40  11.55 

MgO  0.11  0.003  [  0.202  1.98    H2O  0.63  0.92 

CaO  9.34  0.167)  TOOOO  100.00 

Cl  0.24  0.007 


Ign.        0.57  +  9  =  0.063  [  a°70    °-70 
JX          0.35 
100.03 

*  Geol.  For.  Forhandl.,  vi,  p.  537,  1883.  t  Ibid.,  p.  663. 

t  X  =  CuO  0.02,  A1208  0.07,  Fe2Os  0.12,  alkali  0.10,  Pa06  0.04. 


FROM  FRANKLIN,  N.  J.  337 

The  ratio  of  SiO2 :  PbO  :  CaO  :  (OH  +  Cl)  =  3.00  :  3.02  : 
1.98  :  0.70,  or,  excepting  the  hydroxyl  and  chlorine,  a  very 
close  approximation  to  3:3:2:1,  thus  agreeing  with  the 
ratio  of  nasonite.  The  water  (loss  on  ignition)  is  low,  owing 
undoubtedly  either  wholly  or  in  part  to  the  partial  oxidation 
of  the  manganese  during  ignition.  It  is  also  possible  that 
a  trace  of  fluorine  was  present,  since  the  amount  necessary 
to  bring  the  ratio  of  (OH  +  Cl  +  F)  up  to  1  would  be  trifling 
and  might  easily  be  overlooked.  In  connection  with  Lind- 
strom's  analysis  we  have  given  his  values  recalculated  to  100 
per  cent,  after  substituting  an  equivalent  of  CaO  for  the  small 
amounts  of  MnO  and  MgO,  an  equivalent  of  water  (hydroxyl) 
for  chlorine,  and  disregarding  the  0.35  per  cent  designated  as 
X.  The  theoretical  composition  corresponding  to  the  formula 
Pb4(PbOH)2Ca4(Si2O7)3  is  also  given,  and,  except  for  the 
water,  which  is  0.31  per  cent  low,  the  agreement  between  the 
recalculated  analysis  and  the  theory  is  most  satisfactory. 

Ganomalite  is  tetragonal,  and,  in  all  probability,  nasonite 
crystallizes  in  the  same  system,  for,  as  already  stated,  the 
latter  is  optically  uniaxial  and  breaks  out  into  rude  rec- 
tangular blocks,  corresponding  to  the  form  produced  by  a 
combination  of  the  prismatic  and  basal  cleavages.  The 
cleavage  of  nasonite,  however,  should  be  designated  as  poor, 
scarcely  distinct,  while  ganomalite  is  described  as  having 
distinct  cleavages  parallel  to  the  prism  w(110)  and  the  base. 
Both  minerals  exhibit  strong  positive  birefringence.  The 
specific  gravity  of  nasonite,  5.425,  is  less  than  that  of  ganom- 
alite, 5.738,  which  would  be  expected,  for,  although  nasonite 
contains  chlorine  which  is  heavier  than  hydroxyl,  ganomalite 
contains  more  lead  and  hence  should  be  heavier.  The  per- 
centages of  lead,  according  to  theory  are,  respectively,  nasonite 
67.28  and  ganomalite  68.98.  Thus  in  their  physical  proper- 
ties nasonite  and  ganomalite  are  closely  analogous,  and  it  may 
be  confidently  expected,  on  the  one  hand,  that  if  crystals  of 
nasonite  are  discovered  they  will  be  tetragonal,  thus  con- 
forming to  ganomalite,  while,  on  the  other  hand,  ganomalite 
will  be  found  to  contain  water  in  sufficient  quantity  to  yield 

22 


338  SOME  NEW  MINERALS 

with  the  chlorine  a  ratio  of  SiO2  :  (OH  +  Cl)  =  3  :  1.  The 
two  minerals  furnish  an  excellent  example  of  the  isomorphous 
relation  existing  between  chlorine  and  hydroxyl  in  complex 
molecules,  nasonite  being  essentially  the  pure  chlorine  com- 
pound but  containing  a  trace  of  hydroxyl  (water),  and  ganom- 
alite  being  essentially  the  pure  hydroxyl  compound  but 
containing  a  trace  of  chlorine.  Both  minerals  contain  a 
little  manganese  isomorphous  with  the  calcium. 

Mesosilicic  Acid.  —  The  acid,  H6Si2O7,  of  which  nasonite 
and  ganomalite  are  salts,  is  intermediate  between  orthosilicic 
acid,  H4SiO4,  and  metasilicic  acid,  H2SiOs,  and  it  may  be  re- 
garded either  as  equivalent  to  their  algebraic  sum,  or  as 
derived  from  two  molecules  of  orthosilicic  acid  by  taking 
away  one  molecule  of  water.  The  latter  relation  may  be 
expressed  as  follows: 

Two  molecules  of  Intermediate  or 

orthosilicic  acid.  mesosilicic  acid. 

HO  HO 


HO  HO 

H0  0 

HO 


.  HO 

H0l 


HCr 

The  intermediate  acid  H6Si2O7  is  one  which  has  been  recog- 
nized by  mineralogists,  but  its  salts  have  not  generally  received 
a  prominent  place  in  the  systematic  classifications  of  silicates, 
because  they  are  not  very  numerous.  Groth*  calls  attention 
to  the  acid  and  its  salts,  and  has  given  the  name  "Diortho- 
kieselsaure  "  to  the  acid.  Clarkef  also  has  discussed  the  chem- 
ical relations  of  the  minerals  of  this  group,  adopting  Groth's 
name  diorihosilicic  acid,  and  calling  the  minerals  diorthosili- 
cates.  The  name  diorthosilicic  seems,  however,  inappropriate, 
since  H6Si2O7  is  not  an  orthosilicic  acid  as  the  name  signifies, 
but  a  derivative  of  orthosilicic  acid.  We  feel,  therefore,  war- 

*  Tabellarische  Uebersicht  der  Mineralien,  IV.  Auflage,  p.  105  and  140. 
t  Constitution  of  the  silicates  ;  Bull,  of  U.  S.  Geolog.  Survey,  No.  125,  p.  81. 


FROM  FRANKLIN,   N.   J.  339 

ranted  in  suggesting  new  names,  mesosilicic  for  the  acid  and 
mesosilicates  for  its  salts,  the  prefix  meso  being  derived  from 
/ttecro?,  signifying  middle  or  between.  The  intermediate  rela- 
tion of  mesosilicic  acid  is  evident  from  the  following: 

Orthosilicic  acid,  two  molecules,  H8Si208. 
Mesosilicic  acid,  H6Si207. 

Metasilicic  acid,  two  molecules,    H4Si206. 

The  mesosilicates  are  classed  by  Dana  in  the  small  group  of 
"  Intermediate  Silicates  "  on  page  416  of  his  Mineralogy,  and 
by  Groth  as  "  Intermediare  Silikate "  on  page  138  of  his 
Uebersicht  der  Miner  alien. 

The  commonest  mesosilicate  is  iolite,  the  composition  of 
which  may  be  expressed  as  a  slightly  basic  salt,  as  follows : 
(Mg,  Fe)4Al6(AlOH)2(Si2O7)5,  although  the  two  hydroxyls 
may  be  in  combination  with  the  bivalent  metals  instead  of 
with  the  aluminium.  One  of  the  few  lead  silicates,  barysilite, 
Pb3Si2O7,  is  a  normal  salt  of  mesosilicic  acid,  as  is  also  the 
Franklin  mineral  hardystonite,  Ca2ZnSi2O7,  recently  described 
by  Wolff.*  Hardystonite  is  said  to  occur  at  the  Parker  shaft, 
North  Mine  Hill,  but  we  have  not  yet  observed  it  associated 
with  any  of  the  new  minerals  described  in  the  present  paper. 

4.   LEUCOPHCENICITE. 

This  mineral  made  up  the  larger  part  of  a  specimen  about 
two  inches  in  length  and  breadth  by  one  inch  in  thickness, 
which  was  found  by  Mr.  J.  J.  Me  Govern  of  Franklin,  and 
given  to  C.  H.  Warren  in  1897.  It  has  also  been  observed  in 
small  amount  on  a  few  specimens  sent  to  us  by  Mr.  W.  M. 
Foote.  The  mineral  has  a  crystalline  structure,  vitreous  lus- 
ter, hardness  about  5.5-6,  and  is  conspicuous  on  account  of  its 
light  purplish-red  or  raspberry  color.  It  was  supposed  at  first 
to  be  clinohedrite,  rather  deeply  colored  by  manganese.  It  is 
intimately  associated  with  willemite  of  almost  gem-like  quality 
and  beautiful  light  green  color,  and  with  small  idiomorphic 
crystals  of  brown  vesuvianite,  showing  prisms  of  the  first  and 

*  Proceedings  of  the  Am.  Acad.  of  Arts  and  Sci.,  xxxiv,  479, 1899. 


340 


SOME  NEW  MINERALS 


second  order,  pyramid  of  the  first  order  and  base.  Occasional 
crystal  faces  were  observed  on  the  leucophcenicite,  but  none 
which  gave  any  clue  to  the  system  of  crystallization. 

When  small  fragments  of  the  mineral  are  imbedded  in 
balsam  and  examined  with  the  microscope  it  may  be  seen  that 
the  fragments  are  mostly  irregular,  although  some  are  flat  and 
appear  to  lie  upon  imperfect  cleavage  faces.  There  also  may 
be  seen  irregular  cracks  indicating  a  second  but  not  distinct 
cleavage.  In  polarized  light  the  extinction  seemed  to  be 
slightly  inclined  to  the  direction  of  the  second  cleavage,  and  in 
convergent  light  an  optical  axis  was  observed  near  the  limit  of 
the  field.  The  fragments  showed  a  slight  pleochroism,  pale 
rose  for  vibrations  parallel  to  the  direction  of  cleavage,  and 
colorless  at  right  angles  to  this  direction.  These  properties 
indicate  that  the  material  probably  crystallizes  in  one  of  the 
inclined  systems,  although  wholly  satisfactory  conclusions 
could  not  be  drawn. 

Very  pure  material  for  the  chemical  analysis  was  obtained 
by  crushing  a  portion  of  the  best  specimen,  and  selecting  the 
purest  particles  by  hand.  The  specific  gravity  was  found  to 
be  3.848.  The  results  of  the  analysis  by  Warren  are  as 
follows : 


SiO    .  . 

i. 
.  .  .  26.31 

n. 
26.41 

Average. 

26.36 

] 
0439 

MnO  .  .  . 

.  .  .  60.59 

60.67 

60.63 

0.854 

ZnO   .  .  . 

.  .  .    4.03 

3.72 

3.87 

0.047 

FeO    .  .  . 

trace 

MgO     .  . 

.  .  .     0.21 

0.21 

0005 

CaO  .      . 

.  .  .     5.64 

5.70 

567 

0.101 

Na0O. 

.  .  .     0.39 

039 

0006 

KO 

0.24 

024 

0002  , 

H00  . 

2.70 

2.58 

2.64 

0.146 

Ratio. 


3.03 


1.015        7.00 


1.01 


100.01 


Letting  R  stand  for  the  metals  (chiefly  manganese),  the  ratio  of 
SiO2 :  RO  :  H2O  is  3.03  :  7.00  :  1.01,  or  a  close  approximation 
to  3  :  7  :  1,  and  this  leads  to  the  general  empirical  formula 
H2R7Si3OH.  Since  water  is  not  expelled  from  the  mineral 


FROM  FRANKLIN,  N.   J.  341 

much  below  a  red  heat,  the  hydrogen  must  exist  in  the  form  of 
hydroxyl,  and,  consequently,  the  foregoing  formula  may  be 
written  R5(ROH)/2(SiO4)3  or  as  a  basic  orthosilicate,  exactly 
equivalent  to  humite  except  that  no  fluorine  is  present.  Con- 
sidering the  base  wholly  as  manganese,  the  following  is  sug- 
gested as  a  structural  formula  of  the  mineral,  which  certainly 
appears  simple  and  reasonable.  For  comparison  the  structural 
formula  of  humite  is  also  given. 

Leucophcenicite.  Humite. 

Mn  <g>  Si  <0-Mn-OH        M      O     g.  <0-Mg-(OH,F) 

g>Mg 


0 
Mn<0>Si<0-Mn-OH        MS<0>Si<0-Mg-(OH,F) 

Leucophcenicite  is  therefore  a  manganese  humite,  but  it 
contains  no  fluorine  isomorphous  with  the  hydroxyl.  As 
humite  is  a  magnesium  mineral  resulting  from  metamorphism 
due  to  fumarole  or  pneumatolitic  action,  so  leucophcenicite 
is  a  similarly  constituted  mineral,  produced  probably  by  like 
causes  at  a  locality  where  manganese  was  abundant.  It  is 
probable  that  the  crystallization  of  leucophcenicite  is  analo- 
gous to  that  of  the  minerals  of  the  humite  group,  and,  since  the 
examination  of  fragments  of  leucophcenicite  in  polarized  light 
indicated  one  of  the  inclined  systems  (page  340),  it  may  be 
inferred  that  its  crystallization  is  monoclinic,  with  /3  =  90, 
analogous  to  chondrodite  and  clinohumite,  rather  than  ortho- 
rhombic  like  humite.  Furthermore,  the  discovery  of  this 
mineral  suggests  the  possibility  of  finding  a  series  of  manga- 
nese compounds,  corresponding  to  prolectite,  chondrodite, 
humite,  and  clinohumite.  Attention  may  also  be  called  to 
the  fact  that  Jannasch  and  Locke*  have  described  a  variety 
of  humite  from  Valais,  Switzerland,  exactly  analogous  to 
leucophcenicite  in  that  it  contains  no  fluorine. 

Before  the  blowpipe,  leucophcenicite  fuses  quietly  at  about 
3  to  a  brownish  black  globule.  In  the  closed  tube  it  yields  a 
*  Zeitschr.  fur  anorganische  Chemie,  vii,  p.  92,  1894. 


342          NEW  MINERALS  FROM  FRANKLIN,  N.   J. 

little  water.  Reacts  for  manganese  with  the  fluxes.  The 
powdered  mineral  dissolves  very  easily  in  hydrochloric  acid, 
and  the  solution  yields  gelatinous  silica  upon  evaporation. 

The  name  leucophcenicite  has  reference  to  the  color  of  the 
mineral,  and  was  derived  from  Xeu/co?  =  pale  or  light,  and 
<f>oivt,%  =  purple-red. 

There  are  other  minerals  from  the  locality,  some  of  them 
evidently  new,  which  have  been  partially  examined,  and  it  is 
hoped  that  a  full  description  of  them  may  be  given  in  a  future 
article. 

In  closing  we  desire  to  express  our  thanks  to  those  gentle- 
men, named  at  the  beginning  of  this  article,  who  have  gen- 
erously supplied  us  with  material  for  carrying  on  this 
investigation,  and  especially  to  Mr.  W.  M.  Foote,  who  spent 
some  weeks  collecting  at  the  locality  in  the  summer  of  1898 
and  who  has  called  our  attention  to  a  number  of  interesting 
specimens  and  associations. 


ON  THE   CHEMICAL  COMPOSITION   OF 
SULPHOHALITE. 

BY  S.  L.  PENFIELD. 
(From  Amer.  Jour.  Sci.,  1900,  vol.  9,  pp.  425-428.) 

THE  rare  species  sulphohalite  was  first  described  in  1888  by 
W.  E.  Hidden  and  J.  B.  Mackintosh*  as  a  mineral  of  unusual 
composition,  a  double  sulphate  and  chloride  of  sodium  cor- 
responding to  the  formula  3Na2SO4 .  2NaCl.  It  was  found 
associated  with  the  then  recently  discovered  hanksite,  at  the 
famous  Borax  Lake  locality,  San  Bernardino  County,  Califor- 
nia. It  crystallizes  in  rhombic  dodecahedrons,  belonging  to 
the  isometric  system  and  measuring  at  times  over  30  mm.  in 
diameter.  According  to  information  received  from  Mr. 
Hidden,  only  a  few  specimens  of  the  mineral  were  found. 
Two  of  these  are  in  the  collection  of  Mr.  C.  S.  Bement  of 
Philadelphia,  and  one  in  the  British  Museum,  while  the  type 


FIGURE  1.  FIGURE  2. 

*  Amer.  Jour.  Sci.,  1888,  vol.  36,  p.  463. 


344  ON  THE   CHEMICAL   COMPOSITION 

specimen  from  which  material  for  the  original  analysis  by 
Mackintosh  was  obtained,  was  retained  by  Mr.  Hidden.  This 
latter  specimen  has  been  generously  presented  to  the  writer, 
with  the  understanding  that  part  of  it  should  be  used  for  a 
new  analysis  and  the  remainder  deposited  in  the  Brush  Collec- 
tion of  the  Sheffield  Scientific  School. 

Figures  1  and  2  represent  the  two  specimens  in  the  Bement 
Collection,  natural  size.  The  one  represented  by  Figure  1  is  a 
rhombic  dodecahedron  of  almost  ideal  development,  slightly 
yellowish  in  its  tone  of  color,  and  nearly  transparent.  A  very 
little  gangue,  chiefly  hanksite,  and  a  few  small  crystals  of  sul- 
phohalite  are  the  only  things  attached  to  this  superb  crystal, 
and  the  specimen  can  be  so  held  that  only  small  portions  of 
these  are  visible.  The  second  specimen,  Figure  2  consists  of  a 
group  of  three  large  and  a  few  small  hanksite  crystals  upon 
which  a  number  of  sulphohalite  dodecahedrons  have  grown. 
The  figure  is  merely  a  sketch,  hence  it  is  not  to  be  considered 
as  an  exact  crystal  drawing ;  however,  pains  have  been  taken 
to  represent  the  crystals  in  their  proper  size  and  proportions, 
and,  for  the  sake  of  distinctness,  the  hanksite  crystals  have 
been  stippled.  All  of  the  sulphohalite  crystals  are  distributed 
on  one  side  of  this  specimen  only. 

The  writer's  attention  was  directed  to  the  desirability  of 
reinvestigatiiig  this  species  by  the  following  circumstances : 
In  January  of  the  previous  year,  a  letter  was  received  from 
Prof.  A.  de  Schulten  of  the  University  of  Helsingfors,  Fin- 
land, stating  that  he  had  repeatedly  attempted  to  reproduce 
sulphohalite  artificially,  but  always  obtained  sodium  chloride 
and  sodium  sulphate,,  crystallizing  respectively  as  halite  and 
thenardite.  As  he  was  unable  to  obtain  specimens  of  sulpho- 
halite from  mineral  dealers,  he  appealed  to  the  writer  to  make 
if  possible  a  new  analysis  of  the  mineral,  and,  if  this  should 
conform  to  the  composition  as  given  by  Mackintosh,  he 
expressed  his  determination  to  proceed  with  his  endeavors  to 
make  the  mineral  by  artificial  means.  A  short  time  previous, 
in  an  article  entitled  "  Die  Bildungsverhaltnisse  der  ocean- 
ischen  Salzablagerungen"  by  J.  H.  van't  Hoff  and  A.  P. 


OF  SULPHOHALITE.  345 

Saunders,*  the  probable  non-existence  of  sulphohalite  had  been 
set  forth.  This  decision  was  based  chiefly  upon  the  failure  of 
these  investigators  to  obtain  by  artificial  means  a  double  sul- 
phate and  chloride  of  sodium  corresponding  to  the  composi- 
tion as  given  by  Mackintosh,  their  experiments,  like  those  of 
de  Schulten,  yielding  crystals  of  halite  and  thenardite.  They 
furthermore  endeavored  to  secure  sulphohalite  specimens  from 
dealers,  and  two  small  and  very  expensive  ones  that  were  sent 
to  them  proved  upon  examination  to  be  simply  fragments  of 
halite.  Lastly,  a  request  came  from  Mr.  Hidden  that  the 
present  writer  should  make  a  new  analysis  of  sulphohalite,  for 
the  purpose  of  definitely  establishing  the  identity  of  the 
species  and  its  chemical  composition,  and  the  request  was 
accompanied  by  the  gift  of  the  precious  material. 

The  material  submitted  for  examination  was  part  of  a  rhom- 
bic dodecahedron  which  must  have  originally  measured  about 
30  mm.  in  diameter.  To  it  were  attached  several  small  pris- 
matic crystals  of  hanksite.  The  sulphohalite  material  was  clear, 
transparent,  and  homogeneous,  and  when  tested  with  the  polar- 
izing microscope  it  was  found  to  be  isotropic.  The  fracture  is 
small  conchoidal,  and  the  absence  of  any  distinct  cleavage  is 
noticeable,  thus  distinguishing  it  from  halite.  The  material 
for  analysis,  after  being  carefully  selected  was  crushed  and 
sifted  to  a  nearly  uniform  grain,  and  separated  by  means  of 
methylen  iodide  diluted  with  benzol.  Nearly  all  of  the 
material  ranged  in  specific  gravity  within  the  narrow  limits 
2.493  and  2.506.  The  average  of  these  determinations,  2.500, 
may  be  taken  as  the  correct  specific  gravity,  which  is  close  to 
that  given  by  Hidden  and  Mackintosh,  2.489.  The  material 
thus  separated,  when  tested  with  acid,  gave  no  effervescence, 
thus  indicating  perfect  separation  from  hanksite.  A  few  frag- 
ments, mostly  hanksite,  which  were  heavier  than  the  product 
separated  for  analysis,  effervesced  with  acids,  hence  failure  to 
make  a  complete  separation  from  hanksite  undoubtedly 
accounted  for  the  small  percentage  of  Na2CO3  recorded  in 
Mackintosh's  analysis. 

*  Sitzungsberichte  der  k.  Akad.,  Berlin,  1898,  vol.  1,  p.  387. 


346  ON  THE   CHEMICAL   COMPOSITION 

After  completing  the  quantitative  determinations  of  Cl,  SO8 
and  Na2O,  the  constituents  required  by  the  formula  as  given 
by  Mackintosh,  a  deficiency  was  noted  in  the  analysis,  which 
for  a  time  proved  very  perplexing,  but  led  finally  to  the  dis- 
covery of  another  and  rather  unexpected  constituent,  namely 
fluorine.  In  recording  the  analysis,  sufficient  sodium  has  been 
taken  to  combine  with  the  chlorine  and  fluorine  to  form  the 
molecules  NaCl  and  NaF,  respectively,  while  the  remainder 
of  the  sodium  is  given  as  oxide. 

The  results  of  the  analysis  are  as  follows : 

JResults  of 
Mackintosh. 

42.48 


13.12 
Na2C03          1.77 


The  ratio  of  SO3 :  Na2O  :  Cl :  F  approximates  closely  to  2  :  2  : 
1  :  1,  and  since  the  sodium  (Na)  recorded  is  just  sufficient  to 
unite  with  the  chlorine  and  fluorine,  the  formula  of  sulpho- 
halite  becomes  2Na2SO4 .  NaCl .  NaF.  Fluorine  was  weighed 
as  calcium  fluoride,  and  the  purity  of  the  product  was  proved 
by  converting  it  into  calcium  sulphate.  It  is  interesting  to 
note  the  association  of  this  mineral,  having  three  acid  constit- 
uents, with  hanksite,  which  also  has  three  acid  constituents, 
its  composition,  according  to  the  investigation  of  Pratt,*  being 
9Na2SO4 .  2Na2CO3  .  KCL  Although  the  presence  of  fluorine 
in  sulphohalite  was  wholly  unexpected  and  seemed  at  first 
surprising,  the  occurrence  of  that  constituent  in  some  mineral 
from  the  Borax  Lake  locality  is  not  to  be  wondered  at.  This 
important  deposit  of  borax  has  been  formed  undoubtedly  from 
fumarole  or  solfataric  action,  and  it  is  well  established  that 

*  Page  273. 


Ratio. 

OK 

Calculated  for 
Ja2S04.  NaCl.  NaF. 

41.61 

S03 

41.79 

0.522 

2.00 

Na2O 
K20 

Na 
Cl 

32.37 
0.10 
11.60 
9.10 

0.522 

2.00 

32.25 

11.97 
9.23 

0.256 

0.98 

F 

Ign. 

4.71 
0.15 

0.248 

0.95 

4.94 

99.82 

100.00 

OF  SULPHOHALITE.  347 

volcanic  gases  frequently  give  rise  to  fluorine  as  well  as  to 
boron,  chlorine,  and  sulphuric  acid  compounds. 

Probably  the  name  sulphohalite  would  not  have  been  given 
to  this  mineral  had  its  composition  been  correctly  determined 
by  Mackintosh;  however,  one  would  scarcely  be  justified  at 
the  present  time  in  assigning  a  new  name  to  the  compound. 
To  a  certain  extent  van't  Hoff  and  Saunders  were  correct  in 
calling  attention  to  the  probable  non-existence  of  the  species, 
for,  although  the  mineral  in  name  and  substance  had  an 
existence,  a  double  salt  of  the  composition  3Na2SO4  .  2NaCl 
as  originally  ascribed  to  sulphohalite  is  not  known,  and, 
apparently,  cannot  be  made  by  artificial  means. 

It  is  needless  to  speculate  as  to  how  Mackintosh,  who  was 
an  experienced  and  careful  worker,  made  an  erroneous  analy- 
sis. His  determination  of  SO3  was  nearly  correct,  while  that 
of  chlorine  was  four  per  cent  too  high.  In  one  respect  he 
certainly  made  a  decided  mistake,  namely  in  not  completing 
his  analysis  by  determining  the  amount  of  sodium,  for,  had  he 
done  so,  he  probably  would  have  noted  a  deficiency  and  this 
naturally  would  have  led  to  the  discovery  of  the  missing 
constituent. 

Mineralogists  certainly  are  indebted  to  Mr.  Hidden  for  the 
discovery  of  this  exceptionally  beautiful  and  interesting 
mineral,  while  his  eagerness  to  have  the  species  correctly 
investigated,  together  with  his  generosity  in  supplying  the 
necessary  material  have  enabled  the  writer  to  carry  on  this 
investigation.  Thanks  also  are  due  to  Mr.  Bement  for  the 
loan  of  his  valuable  specimens. 


ON    THE    INTERPRETATION    OF    MINERAL   AN- 
ALYSES:  A  CRITICISM  OF  RECENT  ARTICLES 
ON  THE  CONSTITUTION  OF  TOURMALINE. 

BY  S.   L.   PENFIELD  * 
(From  Amer.  Jour,  of  ScL,  1900,  vol.  10,  pp.  19-32.) 

ABOUT  eighteen  months  have  elapsed  since  H.  W.  Foote 
and  the  present  writer  published  a  joint  article  on  the  chemical 
composition  of  tourmaline,  f  Since  that  time  two  articles  have 
appeared,  presenting  views  differing  from  one  another  and 
from  those  of  Foote  and  the  author ;  one  on  the  Constitution 
of  Tourmaline,  by  Prof.  F.  W.  Clarke  J  of  Washington,  the 
other  Ueber  das  Mischungsgesetz  der  Turmaline,  by  Prof.  G. 
Tschermak  §  of  Vienna. 

In  order  to  discuss  the  views  presented  in  these  articles,  it  is 
desirable  to  carefully  consider  some  facts  concerning  chemical 
analyses.  In  the  first  place,  a  perfect  chemical  analysis  can- 
not be  made.  There  are,  to  be  sure,  a  very  few  analytical 
processes  for  the  determination  of  single  constituents,  which, 
when  carefully  executed,  can  be  relied  upon  to  give  results 
varying  less  than  0.01  per  cent  from  the  theory ;  but  when  it 
comes  to  mineral  analysis,  necessitating  the  splitting  up  of  a 
complex  body  and  the  determination  of  a  number  of  con- 
stituents, such  accuracy  cannot  be  attained.  In  making  a 
mineral  analysis,  one  seldom  feels  confident  that  all  determina- 
tions are  correct,  even  within  0.25  per  cent  of  the  truth, 
although  if  duplicate  analyses  are  made,  it  is  expected  that,  for 
the  majority  of  the  constituents  at  least,  the  two  deter- 
minations will  agree  within  0.10  or  0.20  per  cent  of  one 

*  Only  a  portion  of  this  paper,  treating  of  the  Interpretation  of  Mineral 
Analyses,  is  here  presented.  —  EDITOR. 
t  Page  297. 

t  Amer.  Jour.  Sci.,  1899,  vol.  8,  p.  111. 
§  Mineralog.  und  Petrogr.  Mitth.,  1899,  vol.  19,  p.  155. 


MINERAL  ANALYSES.  349 

another.  At  times,  of  course,  depending  upon  the  difficulty  of 
the  analysis  or  the  scarcity  of  available  material,  variations  of 
0.50  per  cent,  or  even  more,  in  duplicate  determinations  are 
not  to  be  wondered  at. 

Secondly,  analytical  work  may  be  of  a  high  order,  the  results 
very  accurate,  and  yet  an  analysis  may  not  serve  for  the 
determination  of  a  chemical  formula  because  made  on  material 
more  or  less  impure.  The  chemists  of  to-day  have  a  decided 
advantage  over  those  of  a  former  generation,  for  the  micro- 
scope enables  them  to  study  their  material,  select  that  which  is 
best,  and,  if  impurities  cannot  be  avoided,  to  take  their  effect 
into  consideration  in  discussing  the  analytical  results.  Then 
again  the  heavy  solutions  are  invaluable  for  separating  out 
material  for  analysis,  and,  what  is  considered  of  very  great 
importance,  for  furnishing  a  guarantee  of  the  purity  of  any 
given  material ;  for  if  it  can  be  stated  that  all  of  the  mineral 
floats  on  a  solution  of  a  certain  specific  gravity  and  sinks  when 
the  specific  gravity  is  lowered  to  a  trifling  extent,  it  gives  one 
not  only  great  confidence  in  the  purity  of  the  material,  but, 
also,  it  enables  the  investigator  to  present  data  which  others 
may  make  use  of  in  judging  the  character  of  the  work. 

It  has  been  the  author's  privilege  during  the  past  twenty- 
five  years  to  make  many  analyses  of  minerals,  and  to  superin- 
tend the  making  of  many  more  in  the  Sheffield  Mineralogical 
Laboratory ;  also  to  discuss  the  analytical  results  and  derive 
therefrom  the  chemical  formulas  of  minerals,  and  this  occasion 
will  be  taken  to  call  attention  to  certain  features  which  are 
regarded  as  most  important  in  mineralogical  investigations. 
In  the  first  place,  the  utmost  pains  should  be  taken  to  secure 
pure  material,  and,  if  the  results  are  to  be  published,  the  char- 
acter of  the  material  should  be  described,  so  that  its  degree  of 
purity  can  be  judged  by  others.  Secondly,  if  an  analysis  pre- 
sents any  especially  difficult  features,  the  method  of  analysis 
should  be  carefully  described,  and  it  is  in  almost  all  cases  well 
to  give  at  least  some  brief  outline  of  the  analytical  methods 
employed.  Then,  too,  when  material  is  abundant,  it  is  advis- 
able to  make  analyses  in  duplicate,  and  to  give  all  of  the 


350  ON  THE  INTERPRETATION 

determinations,  together  with  the  averages.  Thus  the  inves- 
tigator has  from  beginning  to  end  the  satisfaction  of  a  control 
over  all  determinations,  and,  if  agreements  are  close,  others 
can  form  some  estimate  concerning  the  care  with  which  the 
work  was  executed.  There  are  those  who  apparently  enter- 
tain the  belief  that  closely  agreeing  duplicate  determinations 
indicate  great  accuracy  in  analytical  work,  but  that  is  not 
necessarily  the  case,  for  in  some  analytical  methods  there  is  a 
tendency  for  results  to  come  too  high,  in  others  too  low,  and 
thus  duplicate  determinations,  made  under  like  conditions, 
either  with  faulty  methods,  or  with  good  methods  improperly 
executed,  may  be  uniformly  high  or  uniformly  low,  agreeing 
with  one  another,  and  yet  varying  considerably  from  the  truth. 
Still  two  closely  agreeing  determinations  carry  with  them  a 
certain  weight  which  cannot  be  ignored.  Thirdly,  with  each 
analysis,  the  quotients  obtained  by  dividing  the  several  consti- 
tuents by  their  molecular  or  atomic  weights,  as  the  case 
demands,  should  be  given,  and  from  the  quotients  thus 
obtained  the  ratio  between  the  several  constituents  should  be 
determined.  The  ratio  ought  not  to  be  given  simply  rounded 
out  to  the  nearest  whole  numbers,  but,  taking  the  quotient  of 
the  most  characteristic  or  best  determined  constituent  as 
unity,  the  ratio  should  be  given  to  the  second  place  of 
decimals.  It  is  safe  to  assume  that  the  close  approximation  of 
a  ratio  to  whole  numbers  constitutes  the  strongest  argument 
that  can  be  advanced  in  support  of  the  excellence  of  an  analysis 
and  the  correctness  of  the  derived  formula.  It  will  seldom 
happen  that  a  ratio  approximates  to  whole  numbers  merely  as 
a  matter  of  accident.  Provided  the  compound  is  a  simple  one, 
instead  of  giving  the  ratio,  an  excellent  method  is  to  give  the 
calculated  composition,  which  can  then  be  compared  directly 
with  the  results  of  the  analysis.  Lastly,  for  determining  a 
formula  one  or  two  good  analyses  are  of  more  value  than 
many  indifferent  ones,  hence  it  will  often  prove  best  to  make 
new  analyses  on  material  of  unquestioned  purity.  This  may 
be  done  not  wholly  with  the  idea  that  the  new  analyses  are 
better  than  those  made  by  other  investigators,  but,  knowing 


OF  MINERAL  ANALYSES.  351 

all  about  the  quality  of  the  material  and  the  working  of  the 
analyses,  it  will  be  possible  to  exercise  better  judgment  in 
summing  up  the  results  of  the  investigation,  and  to  present 
with  greater  force  the  arguments  needed  in  support  of  the 
proposed  formula. 

Turning  now  to  the  consideration  of  tourmaline,  two  new 
analyses  were  made  by  Foote  and  the  author,  upon  material  of 
ideal  purity  and  with  the  use  of  most  carefully  studied  methods. 
The  results,  given  on  page  310,  need  not  be  repeated  here,  but 
it  will  be  stated  that,  with  the  exception  of  a  single  water 
determination,  all  constituents  were  determined  in  duplicate ; 
that  in  twenty  out  of  a  total  of  twenty-three  instances,  the 
discrepancy  between  duplicate  determinations  did  not  exceed 
0.10  per  cent ;  and  that  the  maximum  variation  in  the  re- 
maining three  instances  was  0.18  per  cent.  The  single  water 
determination  which  was  not  duplicated  was  controlled  by  a 
closely  agreeing  estimation  of  loss  on  ignition.  In  working 
out  the  ratios  from  these  analyses,  the  method  was  adopted 
of  calculating  for  the  metals  their  equivalent  of  hydrogen, 
including  fluorine  with  hydrogen,  since  tourmaline  contains 
hydroxyl  with  which  fluorine  is  isomorphous.  Thus  the 
ratio  was  found  between  SiO2,B2O8,  and  Total  Hydrogen, 
from  which  the  empirical  formula  of  the  tourmaline  acid  was 
derived.  For  the  sake  of  the  present  discussion  the  ratios 
will  be  repeated  in  two  forms  :  with  one-fourth  of  the  SiO2 
as  unity  and  also  with  one-twentieth  of  the  Total  Hydrogen 
as  unity.  This  latter  method  has  been  here  adopted,  because 
a  few  relations  can  be  brought  out  better  in  the  discussion 
by  so  doing.  The  ratios  of  the  two  analyses  are  then  as 
follows : 

Si02     :       B2O3     :    Total  H.  SiO2      :      B2OS      :    Total  H. 

DeKalb  4.00   :   1.01   :   19.90        402   :   1.01    :   20.00 

HaddamNeck    4.00   :   1.02   :   19.98        4.00   :   1.02   :  20.00 

These  ratios  approximate  very  closely  to  the  whole  numbers 
4  :  1  :  20 ;  such  close  approximations,  in  fact,  are  seldom 
obtained,  and  cannot  in  these  two  instances  be  regarded  merely 
as  matters  of  accident ;  they  are  the  reward,  rather,  of  careful 


352 


ON  THE  INTERPRETATION 


analytical  work  on  material  of  unquestionable  purity.  As 
soon  as  the  ratios  were  worked  out,  it  was  seen  at  once  that  at 
least  one  important  key  to  the  solution  of  the  tourmaline 
problem  had  at  last  been  found :  the  empirical  formula  of  the 
tourmaline  acid  must  be  H^B^Si^O^i- 

And  now,  for  the  sake  of  the  discussion,  some  space  will  be 
devoted  to  the  ratios  derived  from  the  analyses  of  Riggs,  and 
Jannasch  and  Kalb.  These  have  already  been  given  by  Foote 
and  the  author  *  with  |SiO2  as  unity,  and  are  now  repeated, 
together  with  the  ratios  derived  by  taking  ^  Total  Hydrogen 
as  unity.  They  have  moreover  been  arranged  in  series,  com- 
mencing with  the  closest  approximation  to  4  :  20  between  SiO2 
and  Total  Hydrogen,  and  proceeding  to  the  maximum  devi- 
ation from  this  ratio. 


TOURMALINE 

RATIOS   DERIVED   FROM    THE 

ANALYSES  OF  RIGGS. 

No. 
1. 

No.  in  Dana's 
Mineralogy. 

43. 

SiO2 
4.00 

B203 

0.94 

Total  H. 

20.03 

SiO, 

3.99 

:      B208     :    Total  H. 

:    0.94       20.00 

2. 

45. 

4.00 

0.95 

20.03 

3.99 

:   0.95 

20.00 

3. 

48. 

4.00 

1.01 

20.06 

3.99 

:    1.00 

20.00 

4. 
5. 
6. 

47. 
52. 
49. 

4.00 
4.00 
4.00 

0.98 
0.94 
1.01 

20.08 
20.11 
20.12 

3.98 
398 

:    0.97 
:   0.93 

20.00 

?ooo 

3.97 

:   1.00 

20.00 

7. 

36. 

4.00 

0.90 

20.2 

3.96 

:   0.89 

20.00 

8. 

44. 

4.00 

0.88 

20.2 

3.96 

:   0.87 

20.00 

9. 

46. 

4.00 

0.96 

20.2 

3.96 

:   0.95 

20.00 

10. 

42. 

4.00 

0.97 

19.8 

4.04 

:    0.98 

20.00 

11. 

54. 

4.00 

0.98 

19.8 

4.04 

:    0.99 

20.00 

12. 

39. 

4.00 

0.94 

19.7 

4.06 

:   0.95 

20.00 

13. 

41. 

4.00 

0.92 

19.7 

4.06 

:   0.93 

20.00 

14. 

51. 

4.00 

0.91 

19.6 

4.08 

:   0.93 

20.00 

15. 

37. 

4.00 

0.93 

20.5 

3.90 

:   0.91 

20.00 

16. 

38. 

4.00 

0.92 

19.5 

4.10 

:   0.93 

20.00 

17. 

55. 

4.00 

1.01 

20.6 

3.88 

:   0.98 

20.00 

18. 

40. 

4.00 

0.96 

19.3 

4.14 

:    1.00 

20.00 

19. 

50. 

4.00 

0.98 

19.2 

4.16 

:    1.02 

20.00 

20. 

53. 

4.00 

0.97 

18.9 

4.23 

:    1.00 

20.00 

Average 

4.00 

0.95 

19.88 

4.02 

:   0.96 

20.00 

Pages  312  and  313. 


OF  MINERAL  ANALYSES. 


TOURMALINE  RATIOS  DERIVED  FROM  THE  ANALYSES  OF 
JANNASCH  AND  KALB. 


353 


„        HO.  In  .uana'E 
No-      Mineralogy. 

Si03 

B203 

Total  H. 

SiOj     • 

BsO, 

Total  H. 

1.            62. 

4.00 

0.80 

20.00 

4.00 

0.80 

20.00 

2.        64. 

4.00 

0.84 

20.01 

4.00 

0.84 

20.00 

3.         61. 

4.00 

0.95 

20.2 

3.96 

0.94 

20.00 

4.        57. 

4.00 

0.99 

19.8 

4.04 

1.00 

20.00 

5.        56. 

4.00 

0.96 

19.7 

4.06 

0.97 

20.00 

6.        63. 

4.00 

0.98 

19.7 

4.06 

0.99 

20.00 

7.        58. 

4.00 

0.95 

20.4 

3.92 

0.93 

20.00 

8.        60. 

4.00 

0.88 

20.4 

3.92 

0.86 

20.00 

9.        59. 

4.00 

0.92 

18.8 

4.25 

0.98 

20.00 

Average 

4.00 

0.92 

19.9 

4.02 

0.93 

20.00 

Before  entering  upon  the  discussion  of  these  ratios,  let  it  be 
understood  that  the  analysis  of  tourmaline  is  one  of  the  diffi- 
cult problems  of  analytical  chemistry,  and  although  Riggs  made 
duplicate  and  often  triplicate  determinations  of  B2O8  and  H2O 
in  almost  all  cases,  and  duplicated  somewhat  more  than  half 
of  his  determinations  of  SiO2  and  F,  only  single  determinations 
of  other  constituents  are  recorded  in  his  paper,  while  Jannasch 
and  Kalb  record  only  single  determinations.  Also  it  is  to  be 
borne  in  mind  that  although  both  Riggs  and  Jannasch  and 
Kalb  undoubtedly  used  carefully  selected  tourmaline  fragments 
for  analysis,  still  there  is  nothing  to  indicate  that  slight 
amounts  of  foreign  materials  might  not  have  been  present  in 
some  of  the  specimens  analyzed.  Keeping  these  facts  then 
well  in  mind,  let  us  examine  the  ratios  as  presented  in  the  fore- 
going tables.  It  is  granted  that  the  ratios  are  not  exactly  4 : 
1  :  20,  and  to  get  exact  ratios  from  mineral  analyses  is  not  to 
be  expected,  but  the  close  approximation  to  4 :  1 :  20  in  the  case 
of  the  two  analyses  by  Foote  and  the  author,  of  sixteen  out  of 
the  twenty  analyses  by  Riggs,  and  of  eight  out  of  the  nine  ana- 
lyses by  Jannasch  and  Kalb,  constitutes  an  overwhelming  amount 
of  evidence  in  support  of  the  empirical  formula  of  the  tourma- 
line acid,  HaoBaSiiOsi.  It  is  safe  to  state  that  there  does  not 
exist  a  series  of  thirty  silicate  analyses  of  any  one  mineral 
yielding  ratios  which  approximate  so  closely  to  whole  numbers 

23 


354  ON  THE  INTERPRETATION 

as  the  tourmaline  analyses  referred  to  above.  That  some  ana- 
lyses fail  to  yield  a  ratio  as  close  to  rational  numbers  as  desired, 
reflects  discredit  neither  upon  the  analyst  nor  upon  the  char- 
acter of  his  work,  for  the  material  for  analysis  might  not  in  all 
cases  have  been  pure.  Take,  for  example,  No.  17  of  the  series 
of  Riggs,  brown  tourmaline  from  Hamburg,  N.  J.,  occurring 
in  calcite.  The  ratio  of  SiO2 :  Total  Hydrogen— 4 :  20.6. 
Evidently  the  bases  are  too  high,  and  this  particular  analysis  is 
peculiar  in  that  it  shows  5.09  per  cent  CaO,  while  the  next 
highest  percentage  of  CaO  recorded  in  any  of  the.  published 
analyses  is  8.70.  The  material  from  Hamburg  might  well 
have  contained  some  calcite,  either  as  small  included  nodules, 
or  as  an  infiltration  along  cracks,  and  if  the  amount  of  calcite 
be  assumed  as  1.78  per  cent,  equivalent  to  1  per  cent  CaO, 
the  analysis  would  add  up  to  100.82,  which  is  not  too  high 
for  such  a  complicated  substance,  and  the  ratio  of  SiO2: 
Total  Hydrogen  would  become  4.00  :  20.3  or  3.94  :  20.00.  To 
assume  that  the  Hamburg  material  probably  contained  some 
calcite  seems  far  more  reasonable  than  to  speculate,  upon 
some  complex  formula  especially  adapted  to  suit  this  par- 
ticular analysis.  Again,  Nos.  18,  19,  and  20  of  Riggs,  and 
9  of  Jannasch  and  Kalb  indicate  either  that  the  amount  of 
base  is  low,  SiO2  being  assumed  as  practically  correct,  or,  what 
is  far  more  likely,  that  the  amount  of  SiO2  is  too  high,  as  seen 
best  when  one-twentieth  of  the  Total  Hydrogen  is  taken  as 
unity.  Does  the  high  silica  ratio  indicate  that  for  these  special 
cases  a  new  type  of  tourmaline  formula  is  needed,  or  is  it  not 
simpler  to  assume  that  the  material  from  which  these  analyses 
were  made  might  possibly  have  contained  a  little  quartz  or 
other  silicate  as  impurity  ?  It  would  take  not  over  2  per  cent 
of  quartz  as  an  impurity  to  bring  about  the  extreme  amount  of 
variation  from  the  ratio  4  :  20  recorded  in  the  foregoing  tables. 
Summary.  —  As  shown  by  the  tabulation  of  ratios  on  pages 
351  to  353  there  exist  a  series  of  recently  made  and  carefully 
executed  tourmaline  analyses  which  give  ratios  of  SiO2 :  B2O3 : 
Total  Hydrogen  approximating  closely  to  4 : 1 :  20,  from  which 
the  empirical  formula  of  the  tourmaline  acid,  H20B2Si4O21,  is 


OF  MINERAL  ANALYSES.  355 

derived.  That  a  few  analyses  do  not  yield  ratios  agreeing  as 
closely  as  desired  to  4 : 1 :  20  is  not  to  be  wondered  at,  when 
the  difficulties  presented  by  the  analysis  are  taken  into  con- 
sideration, together  with  the  fact  that  the  material  analyzed 
might  not  in  all  cases  have  been  perfectly  pure  and  homo- 
geneous. As  far  then  as  analytical  evidence  may  be  relied 
upon  for  establishing  the  formula  of  a  mineral,  it  may  be  con- 
sidered as  definitely  proved  that  the  empirical  formula  of  the 
tourmaline  acid  is  H20B2Si4O21.  The  science  of  inorganic 
chemistry  has  not  yet  reached  such  a  state  of  development 
that  it  can  be  proved,  as  claimed  by  Tschermak,  that  the 
threefold  formula,  H60B6Si12O68,  is  the  correct  one.  The  em- 
pirical formula  H3oB8Si6O3i,  proposed  by  Clarke,  can  rest  only 
on  the  analytical  evidence  supplied  by  a  few  analyses  of  Riggs 
and  one  by  Jannasch  and  Kalb  which  yield  ratios  approximat- 
ing to  4:1: 19.33  (pages  352  and  353),  and  there  are  good 
reasons  for  believing  that  these  ratios  would  not  be  obtained  a 
second  time  if  the  analyses  were  repeated.  Since  tourmaline 
always  yields  sufficient  water  to  form  two  hydroxyl  radicals, 
it  may  be  considered  as  probably,  if  not  absolutely,  proved  that 
the  formula  of  the  tourmaline  acid  should  be  H18(OH)2B2Si4O19. 
Beyond  this  point  it  seems  safe  only  to  speculate  and  it  cannot 
be  considered  that  the  ideas  presented  are  capable  of  being 
definitely  proved.  All  of  the  analyses  indicate  that  at  least 
half  of  the  hydrogen  atoms  of  the  tourmaline  acid  are  replaced 
by  aluminium,  and  this  fact,  coupled  with  the  idea  that  it 
seems  reasonable  to  unite  the  two  hydroxyl  radicals  with  the 
two  boron  atoms,  led  to  the  suggestion  by  Foote  and  the 
author  (p.  317)  that  the  characteristic  feature  of  all  varieties  of 
tourmaline  is  an  aluminium-borosilicic  acid  H9Al3(BOH)2Si4O19. 
In  this  acid  the  mass  effect  of  the  [Al3(BOH)2Si4O19]  is  re- 
garded as  so  overwhelming  that  it  makes  no  difference  how 
the  nine  remaining  acid  hydrogen  atoms  are  replaced,  whether 
largely  by  aluminium  and  to  a  trifling  extent  by  bivalent 
metals  and  alkalies,  or  largely  by  magnesium  and  to  a  trifling 
extent  by  aluminium  and  alkalies,  the  result  in  all  cases  is 
tourmaline  with  its  characteristic  crystalline  structure.  That 


356  MINERAL  ANALYSES. 

trivalent,  bivalent,  and  univalent  metals,  playing  as  it  were 
the  r6le  of  isomorphous  constituents,  may  unite  in  replacing 
the  nine  hydrogen  atoms  of  the  tourmaline  acid,  is  indeed  a 
remarkable  feature  of  isomorphism,  but  it  furnishes  an  expla- 
nation of  the  composition  of  tourmaline,  and  one  which  can  be 
comprehended,  at  least  to  some  extent. 


ON  SOME  INTERESTING  DEVELOPMENTS  OF 
CALCITE  CRYSTALS. 

BY  S.  L.  PENFIELD  AND  W.  E.  FORD  * 
(  From  Amer.  Jour.  Sci.,  1900,  vol.  10,  pp.  237-244.) 

1.    CALCITE  FROM  UNION  SPRINGS,  CAYUGA  COUNTY,  N.  Y. 

THE  crystals  under  consideration  were  found  during  the 
summer  of  1899  by  Mr.  J.  M.  Clarke,  of  the  Geological  Sur- 
vey of  the  State  of  New  York,  and  were  sent  to  New  Haven 
for  examination.  Mr.  Clarke  had  observed  that  the  crystals 
presented  certain  features  of  unusual  interest,  and  it  was  his 
wish  that  they  should  be  described  and  that  the  specimens 
should  be  deposited  in  the  Yale  Collection.  The  crystals 
occur  in  the  Onondaga  limestone,  in  a  region  where  slight 
tectonic  disturbances  have  taken  place,  giving 
rise  to  fissures  in  which  calcite  has  deposited  as 
vein  material.  The  most  interesting  feature 
presented  by  the  crystals  is  their  diversity  of 
habit,  shown  often  on  a  single  hand  specimen, 
and  due  to  different  methods  of  twinning  to- 
gether with  peculiarities  in  the  development  of 
certain  crystal  faces. 

Most  of  the  crystals  were  not  well  adapted 
for  measurement  with  the  reflecting  goniome- 
ter, but,  using  one  of  the  smaller  ones,  about 
5  mm.  in  length  and  2  mm.  in  diameter,  it  was 
possible  to  identify  the  prominent  forms  by 
means  of  their  angles.  The  small  crystals  are 
quite  highly  modified  and  their  development 
is  represented  by  Figure  1.  The  terminal  faces  FIGURE  1. 

*  Reprinted  in  part. —  EDITOR. 


358  ON  SOME  DEVELOPMENTS 

are  the  brightest  and  best  developed,  and  are  those  of  the 
common  scalenohedron  v  (2131).  There  was  measured  for  the 
identification  of  this  form  r  (cleavage)  A  v,  1011  A  2131  =  28°  56', 
calculated  29°  V  30".  In  the  zone  r,  v,  and  making  a  very 
small  angle  with  v  is  the  scalenohedron  vl  (7.4.11.3)  which  is 
especially  prominent  on  the  crystals  from  this  locality.  This 
form  was  identified  by  von  Bournon  on  crystals  from  Derby- 
shire and  the  Dauphine  Alps,  and  appears  as  form  No.  37, 
Plate  31,  of  his  Traite  de  Mineralogie,  published  in  1808.  The 
form  was  identified  by  its  position  in  the  zone  r,  v,  and  the 
measurement  v  A  v\  =  3°  23',  calculated  3°  55'.  On  the  crystals 
under  consideration  the  faces  of  the  scalenohedron  vi  have  a 
vicinal  development,  and  thus  the  contrast  between  them  and 
the  better  developed  faces  of  the  scalenohedron  v  is  generally 
quite  marked.  A  negative  rhombohedron,  /i,  truncates  the 
edges  of  vi  and  appears  always  as  a  narrow  face  with  vicinal 
development  from  which  no  reflection  could  be  obtained.  A 
rhombohedron  in  this  position  would  have  the  symbol 
(0.12.12.5)  and  is  a  little  steeper  than  the  common  rhom- 
bohedron /  (022l),  which  truncates  the  pole  edges  of  the 
scalenohedron  v.  The  pyramid  of  the  second  order  7  (8.8.18.3) 
was  identified  by  the  measurement  8.8.1B.3  A  8.8.16.3  =  25°  40', 
calculated  24°  46',  and  further,  by  its  being  truncated  by  the 
positive  rhombohedron  M,  (4041).  This  rare  pyramid  was 
first  identified  by  vom  Rath*  on  crystals  from  Andreasberg  in 
the  Harz,  and,  as  pointed  out  by  the  present  writers,!  this 
same  pyramid  is  the  prevailing  form  of  the  siliceous  calcites 
from  the  Bad  Lands  of  South  Dakota.  On  crystals  from 
Union  Springs  there  is  a  tendency  for  the  upper  and  lower 
faces  of  the  pyramid  7  to  round  into  one  another,  owing  to 
vicinal  development,  and  because  of  this  rounding  it  was 
impossible  to  obtain  an  accurate  measurement  between  the 
upper  and  lower  7  faces. 

On  the  majority  of  the  specimens  the  crystals  are  not  so 
highly  modified  as  the  one  just  described,  but,  as  already  stated, 

*  Fogg.  Annalen,  cxxxii,  p.  521,  1867. 
t  Amer.  Jour.  Sci.,  1900,  vol.  9,  p.  352. 


OF  CALCITE   CRYSTALS. 


359 


the  variation  in  habit  due  to  twinning  and  the  unequal  devel- 
opment of  certain  faces,  gives  to  the  specimens  a  peculiar  inter- 
est. All  the  types  to  be  described  occur  on  a  single  specimen 
having  a  surface  about  half  the  size  of  one's  hand  covered  with 
crystals.  The  crystals  on  this  specimen  were  not  suitable  for 
measurement  and  therefore  no  angles  will  be  given,  but  the 
forms  were  evidently  like  those  identified  on  the  small  crystal 
previously  described. 

Scalenohedral  type.  —  The 
scalenohedron  ^  (7.4.TI.3) 
Figure  2,  is  apparently  very 
common  at  the  locality.  It 
should  be  stated  that  this 
form  has  the  same  middle 
edges  as  the  rhombohedron  r 
(1011)  and  the  common  sca- 
lenohedron v-  (2181)  but  is 
somewhat  steeper  than  the 
latter  form.  A  twinning 
about  the  basal  plane,  Figure 
3,  is  quite  common. 

Twins,  with  the  rhombohe-       FIGURE  2. 
dron  e   (0112)    as    twinning 

plane.  The  habit  resulting  from  this  kind  of  twinning  is  like 
that  of  the  well  known  Guanajuato  calcites,  described  by 
Pirsson,*  and  it  should  also  be  stated  that  as  early  as  1837, 
LeVy  f  also  described  and  figured  oalcite  twins  of  this  same 
type  from  Streifenberg,  Nertschinsk,  Siberia.  Figure  4  (p.  360) 
is  analogous  to  the  figures  of  Pirsson  and  LeVy,  though  drawn 
in  a  different  position,  and  represents  the  common  scaleno- 
hedron v  (2131)  drawn  with  the  twinning  plane  vertical  and 
having  a  position  like  that  of  the  side  face  of  a  cube,  or  the 
pinacoid  010  of  any  of  the  three  axial  systems.  This  position 
has  been  adopted  for  representing  the  twin  crystals  as  it  gives 

*  Amer.  Jour.  Sci.,  1891,  vol.  41,  p.  61. 

t  Description  d'une  Collection  de  Mineraux  formee  par  H.  Heuland,  vol. 
I,  p.  10,  Fig.  5,  Plate  1. 


FIGURE  3. 


360 


ON  SOME  DEVELOPMENTS 


the  best  idea  of  their  peculiar  development.  Figure  5  repre- 
sents the  scalenohedron  vl  (7.4.11.3)  twinned  without  dis- 
tortion, a  type  which  has  not  been  observed  on  any  of  the 
specimens,  but  the  figure  is  introduced  hi  order  to  show  how, 
by  the  extension  of  the  two  lettered  faces  in  front  and  the 
parallel  faces  behind,  together  with  the  suppression  of  the 
four  small  faces  below,  the  Guanajuato  type,  Figure  4,  results. 


FIGURE  4. 


FIGURE  6. 


FIGURE  6. 


Most  of  the  Union  Springs  crystals  of  the  Guanajuato  type 
show  in  addition  to  the  scalenohedron  certain  modifications 
at  the  reentrant  angle,  Figure  6.  The  faces  forming  the 
reentrant  angle  are  the  pyramid  of  the  second  order  7 
(8.8.16.3)  and  a  rhombohedron  designated  as  A,  apparently 
in  the  zone  with  v1  and  7,  which  would  cause  it  to  have  the 
symbol  (8083).  The  surfaces  forming  the  gash  or  reentrant 
angle,  however,  are  curved  to  such  an  extent  that  exact  sym- 
bols cannot  be  assigned  to  portions  of  them. 

Twins  with  the  rhombohedron  /(0221)  as  twinning  plane.  — 
The  rhombohedron  /  is  one  of  the  rare  twinning  planes  of 
calcite,  and  the  habit  presented  by  the  crystals  from  Union 
Springs  is  very  striking.  The  scalenohedron  vi  (7.4.11.3) 
twinned  about/,  and  drawn  with  the  twinning  plane  vertical, 
as  previously  described,  is  represented  by  Figure  7.  In  the 
Union  Springs  crystals  representing  this  twinning  law  the 
reentrant  angle  at  the  top  wholly  fails,  and  a  peculiar,  pointed, 
spear-head  development,  Figure  8,  results  from  the  extension 
of  the  two  front  lettered  faces  of  Figure  7  and  the  correspond- 
ing faces  at  the  back.  The  crystals  observed  have  always 


OF  CALCITE   CRYSTALS. 


361 


been  attached   at  the   lower  end.     Several   crystals   of   this 
peculiar  type  were  observed  on  the  specimens  sent  by  Mr. 


FIGURE  7. 


FIGURE  8. 


Clarke,  and  they  are  said  to  be  quite  common  at  the  locality. 
On  a  crystal  with  a  broken  point  the  reentrant  angle  measured 
from  the  rhombohedral  cleavages  was  found  to  be  35°  38', 
calculated  35°  27'. 

Le*vy,  in  Figure  6  of  the  atlas  to  his  work  already  cited, 
gives  a  representation  of  a  crystal  from  Kongsberg  in  Norway, 
of  identically  the  same  habit  as  Figure  8  of  this  article ;  how- 
ever, the  habit  is  apparently  a  very  unusual  one,  and  it  is 
interesting  to  record  it  at  a  new  locality. 

On  a  single  specimen  or  even  at  one  locality,  as  a  rule  all 
crystals  of  a  certain  mineral  have  the  same  or  nearly  the  same 
habit,  resulting  undoubtedly  from  crystallization  under  uni- 
form conditions,  and  therefore  it  seems  a  matter  of  more  than 
usual  interest  to  note  on  a  single  hand  specimen  from  the 
Union  Springs  locality,  the  occurrence  of  simple  scaleno- 
hedrons,  Figure  2,  and  of  three  distinct  types  of  twinning, 
Figures  3,  6,  and  8.  The  calcite  crystals  seem  to  be  all  of  one 
generation.  Associated  with  them  are  a  few  crystals  of  dolo- 
mite, apparently  of  later  growth. 


362 


ON  SOME  DEVELOPMENTS 


2.    BUTTERFLY    TWINS    FROM    EGREMONT,  CUMBERLAND, 

ENGLAND. 

The  so-called  butterfly  twins  from  Egremont  are  well-known 
and  are  figured  in  many  mineralogies.  Le*vy  in  his  work, 
already  cited,  gives  three  figures  of  them,  No.  17,  68,  and  69 
of  his  atlas.  A  few  words  concerning  them  and  new  figures 
are  introduced  in  the  present  article  for  the  sake  of  compari- 
son with  the  two  types  of  rhombohedral  twinning  previously 
described.  The  twinning  plane  in  these  crystals  is  the  rhom- 
bohedron  r  (1011),  and  the  common  scalenohedron  v  (2131) 
thus  twinned,  and  drawn  as  in  previous  cases  with  the  twin- 


FIGURE  9. 


FIGURE  10. 


ning  plane  vertical,  is  represented  by  Figure  9.  Figure  10 
represents  a  crystal  of  the  butterfly  twin  type  in  the  Brush 
Collection,  and,  by  comparison  with  Figure  9,  it  may  be  seen 
that  the  upper  faces  of  the  crystal  result  from  the  develop- 
ment of  the  two  front,  lettered  faces  of  Figure  9  and  corre- 
sponding faces  behind,  to  the  complete  obliteration  of  the 
reentrant  angle.  The  faces  at  the  lower  extremity  of  Figure 
10  are  those  of  the  prism  m,  (1010). 

It  is  a  matter  of  interest  to  observe  how  the  scalenohedron, 
when  twinned  as  described  according  to  the  three  rhombo- 
hedral laws,  gives  apparently  simpler  shapes  by  distortion,  or 
unequal  development  of  some  of  its  faces,  than  if  the  distor- 
tion had  not  taken  place. 


OF  CALCITE   CRYSTALS. 


363 


3.  CRYSTALS  FROM  PALLAFLAT,  CUMBERLAND,  ENGLAND. 

A  feature  of  the  crystals  from  this  locality,  as  represented  by 
specimens  in  the  Brush  Collection,  is  the  prominent  development 
of  the  negative  scalenohedron  #(1341).  This  form,  as  shown 
by  Figure  11,  has  its  shorter  pole  edges  bevelled  by  the  common 
scalenohedron  v(  2131)  and  has  the  same  middle  edges  as  the 
negative  rhombohedron,  /(0221).  Figure  11  was  drawn  by 
Mr.  W.  Valentine  of  the  Sheffield  Laboratory.  It  presents 
nothing  new,  and  is  practically  identical  with  Figure  674  of 
von  Bournon's  Traite  de  Mineralogie,  published  in  1808.  The 
figure  is  introduced  in  the  present  article,  because  by  under- 
standing its  simple  zonal  relations,  the  same  forms  can  be 
easily  identified  as  they  occur  on  a  twin  crystal  to  be  described. 

Figure  12  represents  the  development  of  two  beautiful  twin 
crystals  in  the  Brush  Collection,  both  occurring  on  the  same 
hand  specimen.  The  twinning  plane  is  the  unit  rhombohe- 
dron, and  the  development  is  analogous  to  that  of  the  butterfly 
twins  from  Egremont,  Figure  10.  A  prominent  feature  of  the 


FIGURE  11. 


FIGURE  12. 


twins  is  the  vertical  zone  r,/,  and  x  of  the  individual  to  the 
right,  extending  over  the  twinning  plane  to  x,  /,  and  r  of 
the  left-hand  individual,  and  so  on  around  the  crystal.  Thus 
with  this  method  of  twinning,  four  x  faces,  two  in  front  and 


364       SOME  DEVELOPMENTS   OF  CALCITE  CRYSTALS. 

two  behind,  form  as  it  were  a  vertical  prism,  analogous  to 
the  prism  formed  by  four  faces  of  the  scalenohedron  v,  Figure 
4,  when  the  flat  rhombohedron  e(01l2)  is  the  twinning  plane. 
In  Figures  4  and  12  the  rhombohedral  symmetry  is  not 
apparent,  and  the  habit  is  like  that  of  twin  crystals  of  the 
monoclinic  system,  having  the  vertical  faces  v  and  z,  respec- 
tively, as  prisms  and  a  pinacoid  as  twinning  plane.  The  twin 
crystals  represented  by  Figure  12  are  so  attached  that  only  a 
portion  of  the  lower  x  and  v  faces  are  visible. 


ON  THE  CHEMICAL  COMPOSITION   OF 
TURQUOIS. 

BY  S.  L.  PENFIELD. 
(From  Am.  Jour.  Sci.,  1900,  vol.  10,  pp.  346-350.) 

THROUGH  the  kindness  of  Mr.  Ernest  Schernikow  of  New 
York  City,  the  writer  has  recently  received  a  suite  of  turquois 
specimens  from  deposits  in  Los  Cerillos  Mountains,  New 
Mexico,  and  the  Crescent  Mining  District,  Lincoln  Co.,  Ne- 
vada, and  one  fragment  of  exceptionally  fine  quality  from  the 
last-named  locality  was  presented  with  the  special  request 
that  it  should  be  used  for  chemical  analysis.  The  material 
was  very  fine-grained,  of  a  beautiful  robin's-egg  blue  color, 
and  broke  with  a  smooth  fracture.  A  thin  section  of  the 
material  appeared  translucent  and  almost  colorless,  and  when 
examined  under  the  microscope,  the  turquois  seemed  to  be 
perfectly  uniform,  showing  no  evidence  of  being  made  up  of 
two  substances,  such,  for  example,  as  an  aluminium  phosphate, 
mixed  with  a  copper  salt  as  coloring  material.  The  material 
was  so  fine-grained  that  no  clue  as  to  its  crystallization  could 
be  made  out  other  than  that  it  acted  somewhat  on  polarized 
light.  The  specific  gravity,  taken  by  suspension  in  the  heavy 
solution,  was  found  to  be  2.791. 

In  considering  the  chemical  composition  of  turquois,  it 
should  be  borne  in  mind  that  analyses  have  been  made  of  only 
massive,  cryptocrystalline  fragments,  and  although  they  may 
be  selected  ever  so  carefully  no  such  guarantee  of  the  purity 
of  the  material  can  be  given  as  when,  for  example,  a  well 
crystallized  mineral  is  analyzed.  In  order  to  show,  however, 
that  turquois  is  a  material  of  nearly  uniform  composition,  the 
new  analysis  is  given  below  in  connection  with  analyses  made 
by  other  investigators.  Analyses  have  not  been  included 


366  ON  THE   CHEMICAL 

which  show  a  large  proportion  of  foreign  constituents  other 
than  silica.     The  analyses  are  as  follows : 


I.                   II.  III.                  IV.  V.                   VI.                 VII. 

icoln  Co.,  Nichabour,  Karkaralinsk,  Fresno  Co.,            T      r     .,,       N       Moiripn 

Nevada.          Persia.  Russia.  California.                            J°8'  New  Mexico' 

Penfield.        Church.*  Nicolajew.t  Moore.t                Three  analyses  by  Clarke.§ 


P206  34.18  32.86  34.42  33.21  31.96  32.86  28.63 

A1203  35.03  40.19  [35.79]  35.98  39.53 1       36.88  37.88 

Fe203  1.44  2.45 1|  3.52  2.99  .  .  .  2.40            4.07 

CuO  8.57  5.27  7.67  7.80  6.30  7.51            6.56 

H2O  19.38  19.34  18.60  19.98  19.80  19.60  18.49 

Insol.  0.93  ...  1.16  0.16            4.20 

X  ...    MnO  0.36  .  .  .  .  .  .     CaQ  0.13     CaO  0.38           .  .  . 

99.53  100.47  100.00  99.96  98.87  99.79  99.83 

Sp.  gr.  2.79  2.75  2.89  2.86  2.80 

In  the  new  analysis  the  iron  was  found  to  exist  wholly  in 
the  ferric  condition,  and  therefore  the  iron  in  Church's  analy- 
sis, given  as  FeO  in  the  original  article,  has  been  calculated  to 
Fe2O3  to  agree  with  the  observations  of  the  present  writer  and 
other  investigators. 

It  is  evident  from  an  examination  of  the  foregoing  analyses 
that  turquois  is  a  material  which  is  quite  uniform  in  its 
chemical  composition,  so  uniform  in  fact  that  it  does  not 
seem  reasonable  to  consider  it  as  an  accidental  mixture  of  an 
aluminium  phosphate  and  a  copper  phosphate.  The  presence 
of  the  bivalent  element  copper,  however,  in  somewhat  variable 
amounts,  is  not  so  easily  accounted  for  if  we  are  to  consider  a 
copper  phosphate  as  isomorphous  with  an  aluminium  phos- 
phate. The  small  amount  of  iron  is  probably  isomorphous 
with  the  aluminium,  and  it  is  to  be  expected  that  the  iron 
phosphate  would  have  little  effect  upon  the  color  of  the  stone, 
for  the  hydrated  ferric-phosphate,  strengite,  and  the  hydrated 
ferric-arsenate,  scorodite,  are  both  light-colored  minerals.  The 
idea  that  the  iron  is  present  as  the  hydrated  oxide,  limonite, 
can  scarcely  be  entertained. 

*  Chemical  News,  x,  p.  290,  1864. 

t  Kokscharow's  Min.  Russland,  ix,  p.  86,  1884. 

\  Zeitschr.  Kryst.,  x,  p.  247,  1884. 

§  Amer.  Jour.  Sci.,  1866,  vol.  32,  p.  212. 

||  Given  as  2.21  per  cent  FeO.  If  Includes  some  Fe208. 


COMPOSITION  OF  TURQUOIS, 


367 


An  important  factor  to  be  taken  into  consideration  in 
discussing  the  analyses  is  that  the  hydrogen  in  turquois  is  to 
be  regarded  as  representing  hydroxyl  and  not  water  of  crystal- 
lization, for  water  is  not  expelled  from  the  mineral  at  a  low 
temperature;  hence  hydroxyl  radicals  may  be  considered  as 
playing  a  part  in  the  chemical  composition  of  the  mineral. 
Considering  copper  as  an  essential  constituent  of  turquois 
and  not  as  an  impurity,  two  theories  naturally  suggest 
themselves:  one,  that  the  bivalent  copper  is  isomorphous 
with,  and  replaces  the  bivalent  aluminium-hydroxide  radical 
[A1OH]" ;  the  other,  that  the  univalent  copper-hydroxide  rad- 
ical [CuOH]'  is  isomorphous  with  the  univalent  aluminium- 
hydroxide  radical  [A1(OH)2]'.  The  first  of  these  ideas  has 
led  to  no  satisfactory  solution  of  the  problem;  the  second, 
however,  reveals  a  constancy  in  the  chemical  relations  of  the 
mineral  which  can  scarcely  be  regarded  as  due  to  accident. 
The  relations  in  question  are  shown  by  combining  aluminium 
and  iron  with  two  hydroxyls  to  form  the  groups  [A1(OH)2] 
and  [Fe(OH)],  respectively,  and  copper  with  one  hydroxyl 
to  form  the  group  [CuOH],  and  then  finding  the  ratio 
between  the  phosphorus  and  [A1(OH)2]'  +  [Fe(OH)fi]'  + 
[CuOH]'  +  Excess  of  Hydrogen.  The  relations  are  shown 
by  the  ratios  derived  from  the  several  analyses  tabulated  on 
the  previous  page,  as  follows : 


i. 

p 

0.482 

Al(OH), 

0.686  x 

Fe(OH)2 

0.018  (       _0 

Cu(OH) 

0.108  ( 

H 

0.638  >> 

n. 

m. 

0.462 

0.484 

0.788  N 

0.702  x 

0-028  f 
0.066  p332 

0.044  I 

0.096  fL32° 

0.450' 

0.478' 

IV. 

0.468 


Al(OH),  0.706  v  0.774 

Fe(OH)2  0.036  I  ..  . 

Cu(OH)  0.098  (  '    0.080 

H  0.638 )  0.572 


V.  VI. 

0.450  0.464 

0.722  x 

°-030  ll 

1- 


1 

L 


0.094  ( 
0.582' 


0.742 


0.083 
0.387 


VII. 

0.404 


368  ON  THE   CHEMICAL 

Considering  [A1(OH)2]'  +  [Fe(OH)2]'  +  [CuOH]'  +  H 
as  playing  the  role  of  a  univalent  radical  R',  the  ratios  of  P :  R 
in  the  several  analyses  are  as  follows : 

I,  P  :  E,  =  0.482  :  1.450  =  I  :  3.01 
II,    «     "  =  0.462  :  1.332  =  1  :  2.88 

III,  "     "  =  0.484  :  1.320  =  I  :  2.73 

IV,  "     "  =  0.468  :  1.478  =  1  :  3.16 
V,    «     "  =  0.450  :  1.426  =  1  :  3.17 

VI,    "     "  =  0.464  :  1.428  =  1  :  3.08 
VII,    "     "  =  0.404  :  1.262  =  1  :  3.12       Average  =  1  :  3.02 

The  author  can  vouch  for  the  purity  of  the  material  ana- 
lyzed by  him,  as  far  as  it  is  possible  to  do  so  in  the  case  of  a 
cryptocrystalline  mineral,  and  can  also  testify  as  to  the  accu- 
racy of  the  analysis ;  hence  the  very  close  approximation  to 
the  exact  ratio  1  :  3,  between  the  phosphorus  and  the  sum  of 
the  univalent  radicals  plus  the  hydrogen,  is  very  suggestive. 
The  ratios  in  the  other  analyses  approximate  as  closely  to 
1  :  3  as  might  be  expected  when  the  character  of  the  material 
is  taken  into  consideration,  and  the  average  of  all  the  ratios 
is  almost  exactly  1  :  3.  The  ratio  1  :  3  is  that  of  phosphorus 
to  hydrogen  in  orthophosphoric  acid,  H3PO4.  Turquois  may 
therefore  be  regarded  as  a  derivative  of  orthophosphoric 
acid  in  which  the  hydrogen  atoms  are  to  a  large  extent 
replaced  by  the  univalent  radicals  [A1(OH)J,  [Fe(OH)J  and 
[CuOH].  There  seems  to  be  no  fixed  ratio  between  the 
radicals  [A1(OH)2],  Fe(OH)2]  and  [CuOH],  nor  between 
the  sum  of  the  hydroxyl  radicals  and  the  hydrogen.  In  some 
cases,  however,  there  is  an  approximation  to  the  ratio  2  :  1 
between  the  sum  of  the  hydroxyl  radicals  and  the  hydrogen, 
as  follows : 

[A1(OH)2]  +  [Fe(OH)2]  +  [CuOH]  H 

II,  0.882  :         0.450  =  2  :  1.02 
III,                         0.844                         :         0.478  =  2  :  1.13 

VII,  0.875  :         0.387  =  2  :  0.89 

In  cases  like  the  foregoing,  the  composition  of  tur- 
quois  might  be  considered  as  a  mixture  of  an  aluminium 


COMPOSITION  OF  TURQUOIS.  369 

salt,  H[A1(OH)2]2PO4,  with  the  isomorphous  molecules 
H[Fe(OH)2]2PO4  and  H[CuOH]2PO4.  The  molecule 
H[A1(OH)2]2PO4  is  equivalent  to  Clarke's*  formula  for 
"  normal  turquois,"  2A12O8 .  P2O6  .  5H2O,  which  he  also  writes 
A12HPO4(OH)4.  Adopting  Clarke's  suggestion  that  turquois 
contains  very  finely  divided  admixtures  of  iron  and  copper 
phosphates  as  impurities,  and  also  his  formula  for  the  pure 
mineral  (normal  turquois  of  Clarke),  Groth  f  expresses  the 
composition  as  PO4A12(OH)3  .  H2O  but  suggests,  however, 
that  the  formula  is  perhaps  PO4H[A1(OH)2]. 

In  conclusion  it  may  be  stated  that  it  is  the  author's  belief 
that  copper  and  the  small  amounts  of  iron  are  to  be  regarded 
as  constituents  of  turquois,  rather  than  as  impurities.  In  sup- 
port of  this  idea  the  constant  occurrence  of  copper,  as  shown 
by  all  the  published  analyses,  may  be  cited.  Furthermore, 
finely  pulverized  turquois  is  only  partially  dissolved  by  boiling 
in  a  test-tube  with  hydrochloric  acid ;  hence,  if  the  material 
contained  copper  phosphate  as  an  impurity,  it  would  be 
expected  that  the  copper  phosphate  would  dissolve  readily, 
leaving  the  basic  aluminium  phosphate  as  a  pure  white  residue, 
while  in  tests  which  have  been  made  the  insoluble  residues 
have  remained  blue  from  beginning  to  end  of  the  experiments. 
Considering  the  existence  in  turquois  of  the  univalent  radicals 
[A1(OH)2],  [Fe(OH)2]  and  [CuOH],  the  composition  of 
the  mineral,  as  shown  by  the  published  analyses,  may  be  ex- 
pressed as  a  derivative  of  orthophosphoric  acid,  as  follows : 

[Al(OH)2,Fe(OH)2,Cu(OH),H]3P04. 

The  [A1(OH)2]  radical  always  predominates,  but  is  not 
present  in  fixed  proportion.  Some  analyses  (II,  III,  and  VII) 
conform  closely  to  the  formula[Al(OH)2,Fe(OH)2,Cu  (OH)]2 
HP04. 

Disregarding  the  iron,  the  calculated  composition  of  tur- 
quois for  two  special  cases  of  isomorphous  replacements  are 
given  on  the  following  page : 

*  Loc.  cit. 

t  Tabellarische  Uebersicht  der  Mineralien,  1898,  p.  97. 
24 


370 


COMPOSITION  OF  TURQUOIS. 


[Al(OH)2,Cu(OH),H]8PO4  ;               Analysis  I, 
A1(OH)2  :  Cu(OH)  :  H  =  7  :  1*:  6.               page  366. 

P206 

34.64 

34.18 

A1203 

37.32 

36.47* 

CuO 

8.28 

8.57 

H20 

19.76 

19.38 

.  .  . 

Insol.    0.93 

100.00 

99.53 

[Al(OH)2,Cu(OH)]2HPO4  ; 
A1(OH;2  :  Cu(OH  =  12  :  1. 


Analysis  II, 
page  3GG. 


32.13 

42.61 

5.52 

19.74 

10OOO 


32.86 
42.64* 

5.27 
19.34 

MnQ    0.36 
100.47 


Considering  that  turquois  is  not  a  crystallized  mineral,  the 
agreement  between  theory  and  the  analyses  is  certainly  as 
close  as  could  be  expected. 


*  Includes  the  Fe203. 


THE  STEREOGRAPHIC  PROJECTION  AND  ITS 
POSSIBILITIES,  FROM  A  GRAPHICAL  STAND- 
POINT. 

BY  S.  L.   PENFIELD. 
(From  Amer.  Jour.  Sci.,  1901,  vol.  11,  pp.  1-24,  and  115-144.) 

(NOTE.  —  In  the  original  article  of  54  pages,  accompanied  by 
four  plates,  the  possibilities  of  solving  a  large  variety  of  problems 
in  spherical  trigonometry  by  graphical  methods  are  set  forth.  The 
problems  may  be  those  of  crystallography,  astronomy,  geodesy, 
navigation,  or  of  any  nature  whatsoever  where  spherical  relations 
come  into  consideration.  Simple  methods  are  given  for  plotting 
spherical  relations  in  the  stereographic  projection,  and  some  in- 
struments, called  Stereographic  Protractors,  are  described,  by 
means  of  which  the  sides  and  angles  of  spherical  triangles,  thus 
plotted,  may  be  measured.  Only  brief  reference  to  this  article  is 
here  given,  including  the  introductory  paragraphs  and  illustrations 
of  some  of  the  forms  which  the  stereographic  protractors  may 
assume.) 

INTRODUCTION.  The  results  which  are  given  in  the  present 
paper  are  the  outgrowth  of  a  desire  on  the  part  of  the  writer 
to  simplify  some  of  the  processes  of  plotting  and  determining 
crystal  forms.  The  whole  subject  of  stereographic  projection, 
as  it  has  gradually  unfolded  itself  to  him  during  the  past  two 
years,  has  revealed  so  many  possibilities,  and  seems  so  import- 
ant and  of  such  general  interest,  that  it  has  been  decided  to 
present  first  a  paper  treating  of  the  stereographic  projection 
alone,  leaving  for  a  later  communication  its  applications  to 
special  problems  of  crystallography. 

As  far  as  the  mathematical  principles  of  the  projection  are 
concerned,  the  writer  lays  claim  to  no  new  facts.  The  pro- 
jection is  treated,  in  more  or  less  detail  (usually  very  briefly), 
in  most  text-books  of  crystallography,  and  instructions  are 


372  STEREOGRAPHIC  PROJECTION  FROM 

given  for  making  stereographic  projections.  The  processes 
recommended,  however,  are  generally  tedious,  and  one  of  the 
objects  of  the  present  paper  is  to  indicate  how  projections 
may  be  constructed  easily  and  very  accurately.  Moreover, 
no  mathematical  formulas  nor  equations  have  been  used  in 
developing  the  subject,  neither  have  tables  been  employed 
other  than  one  of  natural  tangents  for  calculating  a  certain 
scale.  The  principles  of  the  projection,  as  set  forth  in  this 
article,  are  absolutely  exact;  while  the  errors  involved  in 
solving  problems  by  graphical  methods  are  dependent  upon 
one's  ability  to  locate  points  and  read  scales  correctly,  the 
errors  generally  diminishing  as  the  size  of  the  projection 
increases.  It  is  also  true  of  numerical  calculations  that  the 
processes  are  limited.  Given  exact  data,  results  accurate  to 
the  minute  or  to  the  second  are  obtained  according  as  four- 
place  or  seven-place  logarithm  tables  are  employed ;  while  for 
some  very  exact  geodetic  computations,  where  small  fractions 
of  a  second  must  be  taken  into  consideration,  ten-place 
logarithm  tables  are  at  times  made  use  of.  The  advantages 
of  graphical  methods  over  numerical  calculations  are  numer- 
ous, and  are  fully  appreciated  by  engineers  and  others  who 
deal  extensively  with  measurements  and  practical  results 
derived  therefrom. 

The  writer  would  be  one  of  the  last  to  claim  that  numerical 
calculations  can  be  dispensed  with,  yet  he  contends  that,  for  a 
large  number  of  problems,  especially  those  where  the  data  are 
not  very  exact,  results  obtained  by  graphical  methods  are  in 
every  way  as  serviceable  as  those  secured  by  calculation. 
Then,  too,  it  is  possible  to  make  computations  by  graphical 
methods  wholly  without  the  use  of  formulas  and  tables,  and 
the  processes  can  be  carried  out  intelligently  by  persons  who 
have  had  no  special  mathematical  training,  provided  only  that 
they  have  an  appreciation  of  measurements  expressed  in  terms 
of  degrees  and  fractions.  Many  advantages  to  be  derived 
from  the  use  of  the  stereographic  projection  will  naturally 
suggest  themselves  during  the  course  of  this  paper.  In  sub- 
sequent paragraphs  some  of  these  advantages  will  be  set  forth, 


A    GRAPHICAL   STANDPOINT. 


373 


and  results  obtained  by  plotting  will  be  given,  in  order  that 
an  idea  of  the  accuracy  of  the  method  may  be  obtained. 

The  Stereographic  Protractors. — These   may  be   made  of 


374 


STEREOGRAPHTC  PROJECTION  FROM 


-3 


various  sizes  to  suit  the  requirements  of   different  kinds   of 
work,  and  they  have  this  peculiarity;  that  they  must  be  based 


A    GRAPHICAL   STANDPOINT. 


375 


09} 


00  a 

PS 

*  § 

5  £ 


i 


upon  a  circle  of  the  same  size  as  that  employed  in  making  the 
stereographic  projections  with   which   they  are   to   be   used. 


376 


STEREOGRAPHIC  PROJECTION  FROM 


The  ones  shown  by  Figures  1  to  4  are  based  upon  a  circle  of 
14  cm.  diameter. 


A    GRAPHICAL   STANDPOINT.  377 

Protractor  No.  I,  Figure  1,  may  be  printed  on  card  or 
engraved  on  metal,  and  is  used  for  plotting  stereographic 
relations.  It  has  a  scale  giving  stereographically  projected 
degrees  on  its  diameter  or  base  line,  otherwise  it  is  like  an 
ordinary  protractor. 

Protractors  Nos.  II,  III,  and  IV  are  best  printed  or  engraved 
on  transparent  celluloid.  No.  II,  Figure  2,  consists  of  a 
series  of  stereographically  projected  small  circles,  every  tenth 
degree  of  the  series  being  numbered.  When  this  protractor  is 
centered  and  properly  adjusted  over  a  stereographic  projection 
the  distance  apart  of  any  two  points  may  be  told  by  noting 
their  position  with  reference  to  the  stereographically  projected 
small  circles  of  the  protractor.  Protractor  No.  Ill,  Figure  3, 
gives  a  combination  of  small  circles  and  great  circles.  By 
means  of  it  approximate  solutions  of  problems  (to  within 
a  degree  of  the  truth)  may  be  made.  Protractor  No.  IV, 
Figure  4,  gives  a  series  of  stereographically  projected  great 
circles.  By  centering  it  upon  a  projection  and  turning,  the 
direction  of  the  great  circle  passing  through  any  two  points 
may  be  determined.  For  a  complete  description  of  the  pro- 
tractors and  their  uses,  and  suggestions  concerning  the  appli- 
cations of  the  stereographic  projection  to  accurate  map-making 
the  reader  is  referred  to  the  original  article.  The  protractors, 
various  appliances  for  facilitating  the  construction  of  accurate 
stereographic  projections,  and  extra  copies  of  the  original 
article  may  be  secured  at  the  Yale  Co-operative  Corporation's 
Store  on  the  College  Campus. 


PART  II. -PETROGRAPHY 


EDITED    BY 

L.    V.    PIRSSON 


HISTORY  OF  THE  PETROGRAPHICAL 
DEPARTMENT. 

BY  L.  V.  PIRSSON. 

THE  sciences  of  Mineralogy  and  Petrography  are  most  inti- 
mately related.  Since  Mineralogy  is  dependent  on  chemistry 
on  the  one  hand  and  on  Physics  and  Mathematics  on  the 
other,  so  Petrography  rests  on  Mineralogy  and  Chemistry 
on  one  side  and  on  Geology  on  the  other.  It  sprang  indeed 
from  Mineralogy  and  in  its  earlier  days  before  the  application 
of  Chemistry  and  Geology  brought  forth  those  general  laws 
and  principles  which  give  it  position  as  an  independent 
science,  it  was  a  branch  of  Mineralogy,  microscopical  min- 
eralogy in  fact. 

Thus  we  cannot,  in  one  sense,  positively  state  when  Petrog- 
raphy began  at  Yale.  From  the  days  of  the  elder  Silliman, 
through  the  labors  of  J.  D.  Dana,  of  G.  J.  Brush,  and  of  their 
assistants  and  pupils  in  the  laboratory,  the  ever  increasing  sum 
of  accumulated  mineralogical  knowledge  which  has  made  the 
name  of  Yale  famous  the  world  over  in  this  branch  of  human 
knowledge  has  had  beyond  doubt  an  influence  on  the  de- 
velopment of  the  science. 

But  so  far  as  the  writer  knows,  the  first  investigation  of 
a  rock  and  its  constituents  from  the  petrographic  point  of 
view  was  made  in  1872  by  Professor  E.  S.  Dana  and  pub- 
lished in  the  American  Journal  of  Science.  He  was  at  that 
time  a  student  in  the  laboratory  and  the  investigation  was 
made  on  material  forwarded  by  Prof.  C.  H.  Hitchcock.  This 
resulted  in  the  founding  of  a  new  rock  type  called  Ossipyte. 
This  paper,  from  its  historical  interest,  is  reprinted  as  the  first 
of  those  given  in  this  chapter.  After  this,  during  the  course 
of  his  studies  in  Europe,  Dana  devoted  considerable  time  to 
microscopical  petrography,  which  was  then  just  beginning  to 


382  HISTORY  OF  THE 

attract  the  earnest  attention  of  geologists  and  mineralogists, 
since  it  was  perceived  that  the  microscope  would  lend  them 
powerful  aid  in  the  prosecution  of  their  investigations. 

As  a  result  of  these  studies  he  became  interested  in  petrog- 
raphy and  read  in  1875,  not  long  after  his  return  from 
Europe,  a  paper  on  the  "  Trap  Rocks  of  the  Connecticut 
Valley,"  before  the  American  Association  for  the  Advance- 
ment of  Science,  an  abstract  of  which  appeared  in  their 
proceedings  and  was  also  published  in  the  American  Journal 
of  Science.  This  can  truly  be  said  to  be  the  first  important 
memoir  in  this  science  published  in  this  country  and  to  be  the 
forerunner  of  the  long  series  of  able  investigations  crowned 
with  brilliant  results  which  have  given  American  petrograph- 
ers  the  commanding  position  they  hold  to-day. 

In  his  work  on  the  trap  rocks  of  the  Connecticut  sandstone 
area,  Dana  was  aided  on  the  chemical  side  by  G.  W.  Hawes, 
assistant  in  the  mineralogical  laboratory  to  Prof.  G.  J.  Brush. 
Undoubtedly  this  work  stimulated  the  interest  of  Hawes  in 
this  branch  of  science  and  led  him  to  further  researches  in 
petrography;  the  titles  of  the  papers  giving  the  results  of 
these  researches  are  seen  in  the  appended  bibliography.  The 
lack  of  training  on  the  side  of  microscopical  petrography  is 
seen,  however,  in  the  earlier  work  of  Hawes,  especially  for 
instance  in  his  paper  on  the  greenstones  of  New  Hampshire 
and  their  organic  remains,  in  which  certain  structures  com- 
mon to  such  rocks  were  mistaken  for  fossils  and  therefore 
held  to  indicate  their  sedimentary  origin. 

Feeling  the  need  therefore  of  better  training  in  this  line, 
Hawes  went  abroad  for  study  under  well  known  German 
specialists. 

The  effects  of  this  showed  speedily  in  the  work  he  then 
produced  and  important  papers,  the  results  of  careful  and 
patient  investigations  along  the  line  of  modern  petrography, 
began  to  issue  from  his  pen.  Some  of  these  short  articles, 
from  the  importance  of  the  results  announced  in  them,  have 
become  classics  in  the  science  and  two  of  them  which  hold 
such  a  place  have  been  reprinted  in  this  portion  of  this  work. 


PETROGRAPHICAL   DEPARTMENT.  383 

Hawes,  however,  left  Yale  in  1880  to  go  to  the  National 
Museum  and  his  early  death  soon  after  deprived  the  science 
of  one  of  its  most  sincere,  able,  and  earnest  workers.  A 
short  obituary  of  Hawes,  taken  mostly  from  notices  which 
appeared  at  the  time  of  his  death,  together  with  a  bibliog- 
raphy of  his  works,  is  added  to  these  reprints  of  his  papers. 

After  the  departure  of  Hawes  for  Washington,  an  interval 
of  some  years  elapsed  before  petrographic  work  was  again 
definitely  taken  up  at  Yale,  though  occasional  analyses  of 
rocks  by  Penfield  and  an  important  paper  on  the  Hawaiian 
lavas  by  E.  S.  Dana  based  on  material  collected  by  his  father 
J.  D.  Dana  during  his  visit  to  the  Hawaiian  Islands  in  1887, 
appeared  during  this  period. 

In  1892  the  writer  who  had  prepared  himself  by  study 
under  Rosenbusch  at  Heidelberg  and  Fouqu£  and  Lacroix  at 
Paris,  was  appointed  instructor  in  lithology  in  the  Scientific 
School  and  petrography  was  placed  on  a  definitely  recognized 
basis.  It  is  often  difficult  to  start  a  new  branch  of  the  de- 
scriptive sciences  at  a  new  institution,  but  generally  easy  at 
an  old  and  long  established  one  like  Yale,  where  material  of 
all  kinds  naturally  accumulates.  Thus  through  the  previous 
care  and  interest  of  Brush,  Penfield,  and  the  two  Danas,  the 
writer  was  enabled  to  begin  this  branch  of  science  under  most 
favorable  conditions  as  regards  collections,  library,  etc. 

From  that  time  down  to  the  present  a  considerable  amount 
of  petrographic  work  has  been  done  and  the  collections, 
library,  apparatus  and  the  number  of  students  have  increased 
to  such  a  degree  that  it  is  no  longer  possible  to  occupy 
jointly  the  same  laboratory  with  the  mineralogical  depart- 
ment. Other  quarters  have  therefore  been  provided  and 
now  (1900)  petrography  finds  itself  at  home  in  independent 
quarters  as  a  well  equipped  sub-department. 


384  HISTORY  OF  THE 


BIBLIOGRAPHY  OF  PETROGRAPHICAL  PAPERS  FROM  THE 

LABORATORY  OF  THE  SHEFFIELD  SCIENTIFIC 

SCHOOL  OF  YALE  UNIVERSITY. 

1872.  On  the  Composition  of  the  Labradorite  Rocks  of  Waterville,  New 
Hampshire ;  by  E.  S.  Dana.  Amer.  Jour.  Sci.,  3d  Ser.,  vol.  3, 
pp.  48-50. 

1875.  Trap  Rocks  of  the  Connecticut  Valley;  by  E.  S.  Dana.     Ibid. 

vol.  8,  pp.  390-392.     G.  W.  Hawes,  vol.  9,  pp.  185-192. 

1876.  The  Rocks  of  the  Chlorite  Formation  on  the  Western  Border  of 

the  New  Haven  Region;  by  G.  W.  Hawes.     Ibid.,  vol.  11,  pp. 

122-126. 
The  Greenstones  of  New  Hampshire  and  their  Organic  Remains ; 

by  G.  W.  Hawes.     Ibid.,  vol.  12,  pp.  129-137. 
Igneous  Rocks  in  the  Judith   Mts.,  Montana;  by  E.    S.   Dana. 

Report  of  Reconnaissance  from  Carroll,  Mont.,  to  Yellowstone 

Park  in  1875;  by  Col.  William  Ludlow,  War  Dept.  Washington, 

pp.  105-106. 

1877.  On  grains  of  Metallic  Iron  in  Dolerytes  from  New  Hampshire; 

by  G.  W.  Hawes.     Ibid.,  vol.  13,  pp.  33-35. 

1878.  On  Liquid  Carbonic  Acid  in  Syenite ;  by  G.  W.  Hawes.     Ibid., 

vol.  16,  p.  324. 

Lithology  of  New  Hampshire ;  by  G.  W.  Hawes,  from  Mineralogy 
and  Lithology  of  New  Hampshire,  Geology  of  New  Hampshire. 
Vol.  3,  Part  4,  pp.  262,  Concord,  N.  H. 

1879.  On   a  group   of    dissimilar   Eruptive    Rocks   in   Campton,   New 

Hampshire;  by  G.  W.  Hawes.     Amer.   Jour.   Sci.,  3d  Series, 
vol.  17,  pp.  147-151. 

1881.  The  Albany  Granite,  New  Hampshire,  and  its  Contact  Phenomena; 
by  G.  W.  Hawes.  Ibid.  (3),  vol.  21,  pp.  21-32. 

1884.  Analysis  of  Minerals  from  Hypersthene  Andesite  from  the  Great 

Basin  District;  by  S.  L.  Penfield.     Ibid.,  vol.  27,  p.  459. 

1885.  Analysis  of  Basalt  from  Washoe,  Nev. ;  by  S.  L.  Penfield.     Bull. 

U.  S.  Geolog.  Survey,  No.  17,  p.  33. 

1888.  Analyses  of  Rhyolitic  Obsidian  from  Yellowstone  Park ;  by  S.  L. 

Penfield.     7th  Ann.  Rep.  U.  S.  Geol.  Survey,  p.  282. 

1889.  Contributions  to  the  Petrography  of  the  Sandwich  Islands ;  by  E. 

S.  Dana.     Amer.  Jour.  Sci.  (3),  vol.  37,  pp.  441-467. 
1893.    On  some  Volcanic  Rocks  from  Gough's  Island,  South  Atlantic  ; 

by  L.  V.  Pirsson.     Arner.  Jour.  Sci.  (3),  vol.  45,  pp.  380-384. 
On  the  Geology  and  Petrography  of  Conanicut  Island,  R.  I.  ;  by 
L.  V.  Pirsson.     Ibid.,  vol.  46,  pp.  363-378. 


PETROGRAPHICAL  DEPARTMENT.  385 

1894.  On  some  Phonolitic   Rocks  from  the  Black  Hills;    by  L.   V. 

Pirsson.     Ibid.,  vol.  47,  pp.  341-346. 

1895.  High  wood  Mountains  of  Montana  —  Geology  and  Petrography;  by 

L.  V.  Pirsson  [with  W.  H.  Weed].     Bull.  Geol.  Soc.  Amer., 

vol.  6,  pp.  389-422. 
On  the  Igneous  Rocks  of  the  Sweet  Grass  Hills,  Montana ;  by  L. 

V.  Pirsson  [with  W.  H.  Weed].     Amer.  Jour.  Sci.  (3),  vol.  50, 

pp.  309-313. 
Igneous  Rocks  of  Yogo  Peak,  Montana;  by  L.  V.  Pirsson  [with 

W.  H.  Weed].     Ibid.,  pp.  467-479. 
Complementary  Rocks  and  Radial  Dikes ;  by  L.  V.  Pirsson.    Ibid., 

pp.  116-121. 
On  some   Phonolitic   Rocks   from   Montana;   by  L.  V.   Pirsson. 

Ibid.,  pp.  394-399. 

1896.  The    Bearpaw    Mountains,    Montana,    First    Paper;    by  L.    V. 

Pirsson  [with  W.  H.  Weed].     Ibid.  (4  ser.),  vol.  1,  pp.  283- 

301,  351-362.     Second  Paper,  vol.  2,  pp.  136-148,  188-199. 
A  needed  Term  in  Petrography;  by  L.  V.  Pirsson,     Bull.  Geol. 

Soc.  Amer.,  vol.  7,  pp.  162-163. 
Geology  of  the   Little   Rocky   Mountains,    Montana;   by   L.  V. 

Pirsson  [with  W.  H.  Weed].     Jour.  Geol.,  vol.  4,  pp.  399-428. 
On  the  Monchiquites  or  Analcite  group  of  Igneous  Rocks ;   by 

L.  V.  Pirsson.     Ibid.  pp.   679-690. 
Missourite,  a  new  Leucite  Rock  from  the  Highwood  Mountains, 

Montana;  by  L.  V.  Pirsson  [with  W.  H.  Weed],     Amer.  Jour. 

Sci.  (4),  vol.  2,  pp.  315-323. 
Geology  of  the  Castle  Mountain  Mining  District,  Montana ;   by 

L.  V.   Pirsson  [with  W.  H.   Weed].     Bull.    139,  U.  S.   Geol. 

Survey,  8vo.,  pp.  164. 

1897.  On  the  Corundum  Bearing  Rock  of  Yogo  Gulch,  Montana  ;  by  L. 

V.  Pirsson.     Amer.  Jour.  Sci.  (4),  vol.  4,  pp.  421-424. 

1898.  The  Diabase  of  West  Rock,  Conn. ;  by  L.  V.  Pirsson.     Bull.  150, 

U.  S.  Geol.  Surv.     "Educational  Series,"  pp.  264-273. 
Geology  and  Mineral  Resources  of  the  Judith  Mountains  of  Mon- 
tana; by  L.  V.  Pirsson  [with  W.  H.  Weed].    18th  Ann.  Report 
U.  S.  Geol.  Surv.,  Part  3,  pp.  437-616. 

1899.  On  the  Phenocrysts  of  intrusive  Igneous  Rocks;  by  L.  V.  Pirsson. 

Amer.  Jour.  Sci.  (4),  vol.  7,  pp.  271-280. 
Petrographic  Terms;  by  L.  V.  Pirsson.     Revised  edition  of  the 

International  (Webster's)  Dictionary,  1899-1901. 
Andesites  of  the  Aroostook  Volcanic  Area  of  Maine;  by  H.  E. 

Gregory.     Amer.  Jour.  Sci.  (4),  vol.  8,  pp.  359-369. 

1900.  On  ^Egirite  Granite  from  Miask,  Ural  Mts.  ;  by  L.  V.  Pirsson. 

Amer.  Jour.  Sci.  (4),  vol.  9,  pp.  199-200. 
25 


386  THE  PETROGRAPHICAL  DEPARTMENT. 

Report  on  the  Petrography  of  the  Igneous  Rocks  of  the  Little  Belt 
Mountains,  Montana;  by  L.  V.  Pirsson.  20th  Ann.  Rept.  U. 
S.  Geol.  Survey,  Part  3,  pp.  463-581  (accompanying  report  on 
Geology,  by  W.  H.  Weed). 

On  the  Determination  of  Minerals  in  thin  Rock-sections  by  their 
maximum  Birefringence;  by  L.  V.  Pirsson  [with  H.  H.  Robin- 
son]. Amer.  Jour.  Sci.  (4),  vol.  10,  pp.  260-265. 

Volcanic  Rocks  of  Temiscouata  Lake,  Quebec ;  by  H.  E.  Gregory. 
Ibid.  (4),  vol.  10,  pp.  14-18. 

Geology  of  the  Aroostook  Volcanic  Area  of  Maine;  by  H.  E. 
Gregory.  Bull.  U.  S.  Geol.  Survey,  No.  165,  Part  2,  pp. 
93-188. 


ON  THE   COMPOSITION   OP  THE  LABRA- 

DORITE   ROCKS   OF  WATERVILLE, 

NEW  HAMPSHIRE. 

BY  E.  S.  DANA  * 
(From  Amer.  Jour.  Sci.  (3),  vol.  3,  pp.  48-50.) 

THE  specimens  of  labradorite  rock  which  I  have  had  under 
examination  were  obtained  by  Professor  Dana  last  Septem- 
ber, on  a  visit  with  Professor  Hitchcock  to  the  locality  at 
Waterville,  New  Hampshire. 

There  are  two  distinct  varieties,  both  mentioned  by  Pro- 
fessor Hitchcock  in  the  preceding  article.  The  first  is  a 
dark-colored  rock,  consisting  in  the  main  of  a  triclinic 
feldspar,  together  with  small  yellowish  grains  of  a  mineral 
which  Professor  Brush  in  a  blowpipe  examination  referred 
to  chrysolite.  A  careful  examination  reveals  to  the  eye  also 
some  minute  grains  of  a  magnetic  ore  of  iron,  and  also  a  very 
little  of  a  black  mineral,  probably  hornblende. 

The  feldspar  has  a  dark  smoky  color,  without  iridescence, 
and  is  beautifully  striated.  It  fuses  B.  B.  with  somewhat 
less  readiness  than  ordinary  labradorite,  and  is  scarcely 
attacked  by  acids.  It  was  picked  out  as  carefully  as  pos- 
sible, and  analyzed  with  the  following  result :  — 

*  So  far  as  known,  this  is  the  first  petrographic  study  of  this  rock  type 
consisting  of  labradorite  and  olivine.  It  is  here  definitely  determined,  de- 
scribed and  named.  The  Germans  have  called  such  rocks  "  f orellenstein," 
and  this  has  been  turned  into  "  troctolite  "  by  Bonney  in  1885,  but  ossipite 
has  priority,  and  should  stand. — EDITOE. 


388                      THE  LABRADORITE  ROCKS   OF 

I.  ii.  in. 

Si02  51.04        51.02 

Al208(Ti02)  26.34        26.07 

Fe208  4.79          5.13 

CaO  14.09         14.23 

Na20  3.44 

K90  0.58 


The  large  percentage  of  iron  (determined  volume trically) 
had  not  been  expected,  as  the  eye  had  failed  to  detect  any 
impurities  in  the  fragments  selected  for  analysis.  Some  very 
thin  pieces  were  afterward  examined  under  the  microscope; 
and  by  this  means  it  was  found  that  even  the  clearest  pieces 
contained  very  minute  grains  of  an  iron  ore,  from  -^th  to 
^Tjth  of  an  inch  in  diameter,  which  were  strongly  attractable 
by  the  magnet.  Microscopic  dark  specks  less  than  y^io  o^h 
of  an  inch  in  size  were  also  observed  and  at  first  referred  to 
the  same  cause;  but  on  magnifying  them  800  diameters,  it 
was  concluded  that  they  were  air-cavities  in  the  structure 
of  the  feldspar,  and  not  any  foreign  matter.  The  peculiar 
dark-smoky  color  of  the  rock  is  doubtless  to  be  explained  by 
the  presence  of  these  particles  of  iron  ore. 

This  magnetic  iron  ore,  a  sufficient  amount  for  the  test 
having  been  picked  out  by  the  magnet,  gave  a  decided 
reaction  for  titanic  acid.  It  is,  therefore,  probably  a  very 
magnetic  titanic  iron,  though  it  was  impossible  to  obtain  a 
sufficient  amount  of  the  substance  for  a  quantitative  deter- 
mination of  the  titanium.  The  absence  of  any  octahedral 
faces  or  isometric  structure  in  the  grains  is  in  favor  of  their 
being  titanic  iron. 

In  consequence  of  this  impurity,  which  could  hardly  be 
removed,  it  is  not  to  be  expected  that  the  analysis  should 
give  a  satisfactory  formula;  the  result  obtained,  however, 
is  sufficient  to  prove  that  the  feldspar  is  unquestionably 
labradorite. 

The  analyses  of  the  mineral,  supposed  to  be  chrysolite, 
occurring  in  yellow,  glassy  grains,  afforded :  - 


WATERVILLE,   NEW  HAMPSHIRE.  389 


i. 

H. 

Mean. 

Si02 

38.82 

38.88 

38.85 

A1203 

tr. 

tr. 

tr. 

FeO 

28.00 

28.15 

28.07 

MnO 

1.12 

1.36 

1.24 

MgO 

30.88 

30.36 

30.62 

CaO 

1.26 

1.60 

1.43 

100.08 

100.35 

100.21 

The  oxygen  ratio  of  the  bases  and  silica  afforded  is  nearly 
1 : 1,  and  of  the  iron  and  magnesia  about  1:2;  whence  the 
formula  (JFe  +  JMg)2Si.  This  is  then  a  chrysolite  contain- 
ing an  unusually  large  percentage  of  iron  (here  a  constituent 
of  the  mineral,  and  not  owing  to  the  presence  of  impurities). 
The  amount  of  iron  is  not  strange,  considering  the  fact,  that 
the  rock  contains  diffused  throughout  it  so  much  free 
iron  ore. 

This  chrysolite  has  the  same  ratio  deduced  for  hyalosiderite, 
but  still  differs  widely  in  fusibility  and  other  characters.  It 
is  in  fact  a  true  chrysolite  in  all  respects,  while  hyalosiderite 
is  a  doubtful  compound,  probably  owing  its  fusibility  in 
part  to  the  potash  present.  B.  B.,  the  chrysolite,  is  nearly 
infusible. 

In  two  samples  of  this  labradorite  rock,  obtained  with 
care,  so  as  to  represent  the  average  composition,  1.70  and 
1.94  (mean  1.82)  per  cent  of  MgO  were  obtained,  which 
would  give  5.94  as  the  percentage  of  the  chrysolite  in  the 
whole. 

This  rock,  consisting  of  labradorite  with  grains  of  chryso- 
lite disseminated  through  it,  is  one  not  previously  described. 
Professor  Hitchcock  has  proposed  to  call  it  Ossipyte,  after 
the  name  of  the  tribe  of  Indians  (the  Ossipees)  formerly 
inhabiting  that  region. 

The  second  variety  of  the  rock  (for  position,  etc.,  see  page 
45,  16th  line  from  foot)  presents  quite  a  different  appearance. 
The  feldspar,  here  in  large,  cleavable  masses,  often  half  an 
inch  long,  and  a  dark  mineral,  the  angle  of  whose  cleavage 
planes  proves  it  to  be  hornblende,  form  the  mass;  together 


390       LABRADORITE  ROCKS   OF   WATERVILLE,  N.   H. 

with  these  are  associated  a  magnetic  titanic  iron  in  segregated 
masses  of  some  size,  very  little  of  a  dark  brown  mica,  and  a 
green  mineral,  probably  epidote.  There  is  no  chrysolite. 

This  feldspar  has  a  grayish-white  color,  is  destitute  of 
iridescence,  and  only  careful  searching  reveals  any  striations. 

Two  analyses  afforded :  — 

I.  II.  III.  Mean. 

SiO2  52.15  52.36  .  .  .  52.25 

A1203  27.63  27.39  .  .  .  27.51 

Fe203  1.09  1.07  .  .  .  1.08 

MgO  0.92  1.06  .  .  .  0.99 

CaO  13.10  13.45  .  .  .  13.22 

Na20  ...  ...  3.68  3.68 

K2O  ...  ...  2.18  2.18 

100.91 

Both  analyses  show  that  the  labradorite  of  the  region  is 
remarkable  for  the  large  proportion  of  lime  present. 


GEORGE  W.  HA  WES. 

GEORGE  W.  HAWES  was  born  December  31, 1848,  at  Marion, 
Indiana.  His  parents  died  when  he  was  very  young,  and 
his  early  life  was  spent  at  Worcester,  Mass.  In  1865  he 
entered  the  Sheffield  Scientific  School,  and  remained  till 
the  end  of  his  Junior  year,  when  he  left  to  go  into  busi- 
ness in  Boston.  His  taste  for  science,  however,  led  him  to 
abandon  a  business  career,  and  he  again  entered  the  Sheffield 
School,  and  was  graduated  with  the  class  of  1872.  During 
the  college  year  1872-73  he  was  private  assistant  to  Prof. 
S.  W.  Johnson  in  the  chemical  laboratory,  and  from  1873-78 
he  was  assistant  and  instructor  in  mineralogy  and  blowpipe 
analysis  in  the  Scientific  School.  The  summer  of  1878  he 
spent  at  Breslau  in  the  study  of  microscopical  petrography 
under  Prof.  A.  von  Lasaulx.  He  returned  to  New  Haven 
in  the  fall,  and  again  became  instructor  in  mineralogy,  and 
in  the  spring  went  abroad  the  second  time  for  further  study. 
The  following  year  was  spent  in  the  study  of  mineralogy 
and  crystallography  at  Bonn,  under  Prof.  G.  vom  Rath,  and 
in  petrography  at  Heidelberg,  under  Prof.  H.  Rosenbusch. 
At  the  latter  place  he  took  the  degree  of  Ph.D.  On  his 
return  to  this  country  he  again  took  up  his  old  place  at  New 
Haven,  but  at  the  end  of  the  year  (1880)  he  accepted  the 
position  of  Director  of  the  Geological  Department  of  the 
National  Museum  at  Washington,  which  he  held  up  to 
the  time  of  his  death  from  consumption,  June  22,  1882. 

Hawes  was  one  of  the  earliest  workers  in  petrography  in 
this  country,  and  had  he  lived  he  would  undoubtedly  have 
been  one  of  the  most  distinguished  of  his  time.  He  had 
fitted  himself  by  years  of  careful  study  to  do  the  best  of  work 
in  his  chosen  science,  and  the  quality  of  his  work  is  seen  in 


392  GEORGE    W.   HA  WES. 

his  published  papers.  His  most  important  work  is  his  report 
on  the  mineralogy  and  lithology  of  New  Hampshire,  an 
octavo  volume  of  262  pages,  embodying  the  results  of  con- 
siderable field  work  and  the  preparation  and  study  of  several 
hundred  thin  rock  sections.  At  the  time  of  his  death  he  was 
engaged  in  a  report  on  the  building  stones  of  the  United 
States,  a  work  completed  and  published  later  by  his  succes- 
sor, Prof.  G.  P.  Merrill  of  Washington. 


BIBLIOGRAPHY  OF  G.   W.   HAWES. 

1874.  Analysis    of    Serpentine    Pseudomorphs.     Amer.  Jour.    Sci.,   3d 

Series,  vol.  8,  p.  451. 

On  Feldspar  from  Bamle  in  Norway.     Ibid.,  vol.  7,  p.  579. 
On  the  Chemical  Composition  of  the  Wood  of  Acrogens.     Ibid., 

vol.  7,  p.  585-586. 
Analysis  of  Brucite.     Ibid.,  vol.  8,  p.  453. 

1875.  Trap  Rocks  of  the  Connecticut  Valley.     Ibid.,  vol.  9,  p.  185-192. 
On  Diabantite,  a  chlorite  occurring  in  the  trap  of  the  Connecticut 

Valley.     Ibid.,  vol.  9,  pp.  454-457. 
On  Zonochlorite  and  Chlorastrolite.     Ibid.,  vol.  10,  pp.  24-26. 

1876.  The  Rocks  of  the  "  Chloritic  Formation  "  on  the  Western  Border 

of  the  New  Haven  region.     Ibid.,  vol.  11,  pp.  122-126. 
On  a  Lithia-bearing  variety  of  Biotite.     Ibid.,  vol.  11,  pp.  431- 

432. 
The  Greenstones  of  New  Hampshire  and  their  organic  remains. 

Ibid.,  vol.  12,  pp.  129-137. 

1877.  On  grains  of  Metallic  Iron  in  Dolerytes  from  New  Hampshire. 

Ibid.,  vol.  13,  pp.  33-35. 

1878.  On  Liquid  Carbonic  Acid  in  Syenite.     Ibid.,  vol.  16,  p.  324. 
Mineralogy  and  Lithology  of  New  Hampshire.     Geology  of  New 

Hampshire,  vol.    3,  Part  4,     pp.  262.      Roy.  8vo.     12  Plates. 
Concord,  N.  H. 

1879.  On  a  Group  of  dissimilar  Eruptive  Rocks  in  Campton,  New  Hamp- 

shire.    Amer.  Jour.  Sci.,  3d  Series,  vol.  17,  pp.  147-151. 
1881.    The  Albany  Granite  of  New  Hampshire  and  its  Contact  Phenom- 
ena.    Ibid.,  vol.  21,  pp.  21-32. 

On  Liquid  Carbon  Dioxide  in  Smoky  Quartz.     Ibid.,  vol.  21,  pp. 
203-209. 

[Record  of]  Geology  (for  1879-80),  Smithsonian  Report  for  1880 
pp.  221-234,  1881. 


GEORGE    W.   HAWES.  393 

On  the  Mineralogical  Composition  of  the  normal  Mesozoic  Diabase 
upon  the  Atlantic  Border.  Proc.  National  Museum,  Washing- 
ton, 1881,  pp.  129-136. 

Microscopic  Structure,  10th  Census  U.  S.  Report  on  the  Building 
Stones  of  the  United  States,  and  Statistics  of  the  Quarry  Indus- 
try for  1880,  4to,  pp.  15,  18,  22,  bound  as  part  of  vol.  10,  but 
with  separate  pag.  Washington,  1884. 

Introduction  10th  Census  Report  on  Building  Stones  of  the  United 
States  and  Statistics  of  the  Quarry  Industry  for  1880,  4to, 
pp.  1-14,  bound  as  part  of  vol.  10,  but  with  separate  pag. 
Washington,  1884. 


ON  A  GROUP   OF  DISSIMILAR  ERUPTIVE 

ROCKS   IN  CAMPTON,  NEW 

HAMPSHIRE. 

BY  GEORGE  W.  HA  WES,* 
(From  Amer.  Jour.  Sci.  (3),  vol.  17,  pp.  147-151.) 

AMONG  other  results  of  the  petrographical  studies  made  by 
me  under  the  direction  of  the  New  Hampshire  State  Survey,! 
I  have  shown  that  the  rocks  of  the  dikes,  abundantly  scat- 
tered through  the  White  Mountains,  are  very  diverse  in 
composition  and  in  mineral  constituents.  Independently  of 
the  results  of  decomposition,  which  has  in  many  cases 
widened  original  differences,  rocks  which  to  the  eye  appear 
identical  are  often  found,  on  microscopic  examination,  to  be 
fundamentally  different;  and  the  rocks  of  closely  adjoining 
dikes  not  infrequently  have  nothing  in  common  save  their 
geological  position.  This  feature  is  quite  striking,  especially 
when  considered  in  connection  with  the  uniform  character  of 
the  eruptive  rocks  in  some  adjoining  regions.  To  illustrate 
it  I  have  made  a  study  of  a  small  group  of  dikes  in  Gampton 
where  this  diversity  is  very  well  exhibited. 

The  Livermore  Falls  are  in  Campton,  but  they  are  only 
two  miles  distant  from  the  larger  and  more  accessible  town 
of  Plymouth.  The  Pemigewassett  river  has  here  cut  a  gorge 
through  a  hill,  and  in  the  walls  of  this  gorge  the  eruptive 
dikes  are  very  conspicuous.  The  gorge  is  not  long,  and  the 
dikes,  five  in  number,  are  all  embraced  in  a  portion  of  it 
which  is  little  more  than  a  hundred  yards  in  length. 

*  This  was  the  first  description,  under  the  name  of  "  diorites  and  diabase," 
of  the  interesting  and  important  group  of  rocks  to  which  Rosenbusch  has 
given  the  name  of  Camptonite,  from  this,  the  original  locality.  —  EDITOR. 

t  Geology  of  New  Hampshire,  Hitchcock,  part  iv,  Mineralogy  and  Lithology. 


ERUPTIVE  ROCKS  IN  CAMPTON,  N.  H.  395 

Attention  was  called  to  these  dikes  in  1837,  by  Prof. 
O.  P.  Hubbard  of  Dartmouth  College.*  His  description  of 
them  is  accompanied  by  a  picture  of  the  gorge,  which  shows 
their  forms  and  relative  position ;  but  as  the  rocks  could  only 
be  identified  by  microscopic  examination,  he  did  not  attempt 
to  classify  them. 

The  rock  through  which  the  dikes  intrude  is  mica  schist, 
which  presents  its  usual  diversities,  caused  by  variation  in 
the  proportion  of  the  essential  ingredients  and  the  presence 
of  accessories.  The  strike  is  northeast,  and  the  dip  is  vari- 
able. These  rocks  are  considered  to  be  as  old  as  the  Silurian, 
and  Professor  Hitchcock  regards  them  as  still  older. 

The  five  dikes  cut  the  schist  almost  at  right  angles;  all 
are  nearly  vertical  and  parallel  to  one  another.  A  bridge 
has  been  built  across  the  gorge  from  which  all  the  dikes  can 
be  seen  except  the  one  directly  under  the  bridge.  From 
their  position  with  reference  to  the  schists,  it  is  inferred  that 
the  fractures  resulted  from  the  action  of  the  same  forces 
acting  in  the  same  way.  Yet  among  these  five  dikes  there 
are  found  four  very  well-distinguished  rock  species.  I  will 
describe  these  rocks  in  the  order  in  which  they  occur,  begin- 
ning with  the  one  highest  up  the  stream. 

Dike  No.  1  is  seen  only  upon  the  left  of  the  stream.  It  is 
about  three  feet  wide ;  the  rock  is  black  in  color,  compact, 
and  apparently  nearly  homogeneous.  The  study  of  some 
thin  sections  indicates  that  it  is  a  diabase.  It  was  originally 
a  mixture  of  augite,  a  triclinic  feldspar  and  titanic  iron,  but 
all  its  ingredients  are  partially  altered.  The  augite  is  in 
process  of  alteration  into  hornblende;  some  of  its  grains 
being  still  intact,  some  being  partially  and  others  wholly 
altered.  The  feldspar  is  more  or  less  changed,  but  shows 
its  polysynthetic  character  throughout.  The  titanic  iron 
oxide  is  extensively  altered  into  the  grayish  white  product 
that  is  called  leucoxene.  Minute  apatite  crystals  are  seen 
in  the  section.  Calcite,  as  a  decomposition  product,  fills 
cavities  that  are  apparently  made  by  the  removal  of  some 

*  Amer.  Jour.  Sci.  (1),  vol.  xxxiv,  p.  105. 


396  A    GROUP   OF  ERUPTIVE  ROOKS   IN 

other  mineral;  these  cavities  are  also  often  partially  filled 
with  analcite,  which  has  a  cubic  cleavage  and  exerts  a  very 
feeble  action  upon  polarized  light.  The  analyses  of  all  the 
rocks  described  are  placed  together  on  a  subsequent  page. 

Dike  No.  2  is  eight  feet  wide.  The  rock  is  black  in  color, 
and  is  composed  of  a  very  fine,  almost  homogeneous  ground- 
mass,  in  which  small  black  shining  crystals  are  porphyriti- 
cally  developed.  The  thin  sections  indicate  that  this  is 
diorite.  It  is  a  mixture  of  hornblende,  a  triclinic  feldspar, 
and  titanic  iron  oxide.  The  large  crystals  are  of  hornblende ; 
it  is  here  an  original  product,  and  has  not  resulted  from  the 
alteration  of  pyroxene,  as  in  the  last  case,  since  its  well- 
formed  crystals  are  developed  in  the  common  hornblendic 
forms.  Many  of  them  are  twin  crystals,  the  twinning  plane 
being,  as  usual,  parallel  to  the  orthopinacoid.  Both  the 
large  porphyritic  crystals  and  the  small  ones  in  the  ground- 
mass  are  fresh  and  unaltered.  The  feldspar  is  in  part  fresh 
and  in  part  somewhat  altered.  The  basic  nature  of  this 
rock,  as  of  the  last,  indicates  that  the  feldspar  is  a  variety 
low  in  silica,  but  its  species  cannot  be  determined  by  optical 
means.  The  iron  oxide  is  quite  abundant,  and  in  part  well 
crystallized.  Sometimes  a  large  opaque  hexagonal  section 
is  met  with  which  is  probably  menaccanite.  The  rock  con- 
tains a  little  apatite.  Calcite,  some  zeolitic,  mineral  of  an 
undetermined  species  and  a  little  chlorite  exist  as  decomposi- 
tion products. 

Dike  No.  3  is  ten  feet  wide,  and  is  filled  with  a  massive 
rock  fine  in  texture  and  white  or  grayish  in  color.  When  a 
section  cut  from  a  white  specimen  is  examined,  the  rock  is 
seen  to  be  composed  largely  of  small,  quite  well-defined 
orthoclase  crystals.  The  meeting  of  these  forms  angular 
corners,  that  are  for  the  most  part  filled  with  lime  and  iron 
carbonates  and  chlorite,  though  some  are  filled  with  quartz. 
In  sections  from  the  darker  specimens  it  becomes  evident 
that  the  aggregate  in  the  angles  is  a  decomposition  product, 
for  remnants  of  a  dichroic  green  mineral,  which  is  probably 
hornblende,  are  left  there.  It  contains  in  addition  some 


CAMPTON,   NEW  HAMPSHIRE.  397 

magnetite,  and  some  specimens  show  a  little  pyrite.  The 
rock  is  a  very  fine-grained  syenite  similar  to  those  which 
occur  in  different  parts  of  the  State. 

Dike  No.  4  is  about  a  hundred  feet  from  No.  3,  but  is 
identical  with  it  in  all  respects.  Dike  No.  3  separates  into 
two  branches  in  the  middle  of  the  stream,  and  forms  two 
dikes  in  an  island  there  situated,  and  it  is  not  improbable 
that  No.  4  may  unite  with  it  at  some  point. 

Dike  No.  5  is  about  seventy-five  feet  from  No.  4.  It  is 
very  narrow,  being  only  about  a  foot  wide,  but  it  has  several 
branches  as  wide  as  itself  which  unite  with  it  at  acute 
angles.  This  again,  like  No.  2,  is  composed  of  a  fine-grained 
ground-mass  in  which  larger  crystals  are  developed,  but  when 
the  sections  are  examined  it  is  found  to  be  an  olivine  diabase. 
The  porphyritic  crystals  are  in  part  perfectly  formed  augite 
crystals,  and  in  part  well-formed  olivine  crystals  which  are 
mostly  changed  to  serpentine.  The  finer  portion  of  the  rock 
is  composed  of  augite,  a  triclinic  feldspar,  titanic  iron  and 
minute  brown  dichroic  crystals  of  hornblende.  Some  small 
amygdaloidal  cavities  were  observed  containing  sphaerosid- 
erite,  calcite,  and  analcite. 

In  these  five  closely-adjoining  dikes  there  are,  therefore, 
four  very  different  kinds  of  rocks.  Selecting  specimens  as 
fresh  as  possible  from  the  different  dikes,  I  analyzed  them 
with  the  following  results :  — 

Diabase.      Olivine  Diabase.         Diorite.  Syenite. 

Dike  No.  1.        Dike  No.  5.         Dike  No.  2.  Dikes  Nos.  3  and  4. 

Silica 41.63  42.77  41.94  58.25 

Alumina 13.26  14.06  15.36  18.22 

Iron  sesquioxide  .  .  .  3.19  2.72  3.27  1.07 

Iron  protoxide  ....  9.92  8.34  9.89  5.96 

Manganese  protoxide  0.27  0.15  0.25  0.10 

Titanium  dioxide   .  .  3.95  2.35  4.15  tr. 

Lime 8.86  11.47  9.47  1.51 

Magnesia 7.31  9.72  5.01  tr. 

Soda 2.49  1.89  5.15  4.19 

Potash 3.32  1.43  0.19  5.59 

Carbon  dioxide  ....  5.20  1.62  2.47  4.75 

Water 1.35  2.74  3.29  0.85 

100.75  9^26  100.44  100.49 


398  A    GROUP   OF  ERUPTIVE  ROCKS  IN 

Though  i  have  mentioned  the  existence  of  decomposition 
products,  they  are  present  only  in  minute  quantities ;  and  as 
in  these  very  compact  rocks  the  new  compounds  must  have 
been  formed  from  the  old,  I  think  the  above  analyses  repre- 
sent very  nearly  the  original  composition  of  the  rocks,  with, 
however,  the  addition  of  the  water  and  the  carbon  dioxide. 

Between  the  light  and  dark  colored  rocks  there  is  a  wide 
difference,  which  indicates  that  the  reservoirs  from  which 
they  were  ejected  contained  fused  material  of  very  different 
compositions.  The  black  rocks  are  nearly  alike  in  composi- 
tion, but  their  differences  are  such  as  might  account  for  the 
variation  in  mineral  constituents.  The  quantivalent  propor- 
tion of  the  sesquioxides  to  the  protoxides  is  considerably 
higher  in  the  diorite  than  in  the  diabases,  and  this  is  a  con- 
dition favorable  to  the  formation  of  diorites,  as  shown  by  the 
higher  percentage  of  alumina  usually  found  in  the  hornblende 
of  eruptive  rocks.  The  larger  percentage  of  magnesia  may 
have  favored  the  formation  of  olivine  in  one  diabase  and  not 
in  the  other.  But  the  presence  of  compact  and  porphyritic 
materials  in  different  dikes,  though  of  nearly  the  same  com- 
position, indicates  different  conditions  of  cooling  and  crystal- 
lization, and  these  may  also  have  been  a  cause  of  the  mineral 
distinctions. 

In  the  adjoining  Connecticut  Valley  the  red  sandstones  are 
cut  by  numerous  dikes.  Many  of  these  rocks  and  others  geo- 
logically related  have  been  microscopically  examined  by  E. 
S.  Dana,*  and  some  were  analyzed  by  myself. f  It  was  shown 
that  these  large  dikes  which  are  so  characteristic  of  the  Meso- 
zoic  red  sandstone  of  this  coast  are,  wherever  found,  essen- 
tially uniform  in  composition  and  mineral  constituents.  They 
are  compounds  of  labradorite,  augite,  and  magnetite,  and  vary 
only  in  the  extent  of  their  alteration.  Professor  Dana  has 
concluded  from  this  uniformity  and  their  wide  distribution 
over  the  Atlantic  slope  from  Nova  Scotia  to  North  Carolina, 
that  the  dikes  reach  to  profound  depths. 

*  Amer.  Jour.  Sci.,  Ill,  viii,  390. 
t  Ibid.,  ID,  ix,  185. 


CAMPTON,  NEW  HAMPSHIRE.  399 

It  is  most  probable  that  the  large  and  small  dikes  that  are 
so  common  among  the  crystalline  rocks  of  New  Hampshire, 
occupy  fissures  which  were  made  during  the  elevation  of  the 
mountains.  In  the  process  of  elevation,  variable  conditions 
must  have  been  introduced  in  the  strata  at  different  places 
and  times,  on  account  of  the  conversion  of  mechanical  work 
into  heat,  as  has  been  shown  by  Mallet  and  others,  and  this 
would  have  modified  the  depth  at  which  fused  materials 
would  be  found  beneath  the  surface.  If  partial  crystallization 
took  place  before  eruption,  as  in  the  case  of  many  modern 
volcanic  rocks,  very  variable  conditions  might  also  have  been 
introduced  at  different  times  for  their  solidification.  The 
Mesozoic  sandstones  referred  to  do  not  occupy  a  position  that 
indicates  a  great  strain  upon  the  earth's  crust  at  the  time  of 
fracture,  but  are  found  in  areas  of  gentle  subsidence,  and  the 
uniformity  in  the  dikes  that  characterize  these  regions,  when 
compared  with  the  diversity  in  the  dikes  of  the  mountain  re- 
gion of  New  Hampshire,  is  as  striking  as  is  the  contrast  in 
the  geological  features  of  these  two  areas  of  eruption.  A 
sinking  of  the  earth's  crust  might  result  in  profound  fractures 
which  would  reach  to  the  homogeneous  zone  beneath  the  sed- 
imentary formation.  The  crushing  attendant  upon  elevation 
might  fuse  sedimentary  deposits  at  various  depths,  and  pro- 
duce fissures  that  would  be  filled  with  the  most  diversified 
material. 


THE  ALBANY  GRANITE,  NEW  HAMPSHIRE,  AND 
ITS   CONTACT  PHENOMENA. 

BY  GEORGE   W.   HA  WES. 
(From  Amer.  Jour.  Sci.  (3),  vol.  21,  pp.  21-32.) 

IN  the  studies  that  have  been  directed  to  the  end  of  discov- 
ering the  nature  and  origin  of  our  great  granitic  masses,  the 
contact  phenomena  have  received  but  little  attention.  The 
application  elsewhere  of  the  modern  methods  of  lithological 
research  to  the  rocks  upon  the  limits  of  granitic  masses  has, 
however,  been  fruitful  in  developing  facts  of  geological  inter- 
est. The  study  which  1  present  indicates  that  no  more  strik- 
ing phenomena  have  been  observed  anywhere  than  those 
which  are  found  upon  the  boundaries  of  one  of  the  New 
Hampshire  granitic  masses.  These  phenomena  have  addi- 
tional interest  since  they  occur  in  a  region  of  highly  crystal- 
line schists,  which  usually  are  not  susceptible  to  influences  of 
this  nature.  In  the  Vosges,  for  example,  the  granites,  which 
have  produced  the  most  marked  and  wide-reaching  effects 
upon  clay  slates,  have  had  no  influence  upon  the  crystalline 
schists  which  they  have  intersected.*  As  the  New  Hamp- 
shire granite  here  considered  exhibits  very  striking  modifica- 
tions in  character,  dependent  upon  the  neighborhood  of  the 
contact,  and  as  a  spot  was  found  where  the  arrangement  of 
the  rocks  is  favorable  for  a  careful  consideration  of  the  effects 
of  the  contact  both  upon  the  schists  and  the  granite,  I  have 
investigated  these  rocks  with  a  view  of  presenting  this  study 
as  a  contribution  to  White  Mountain  Geology. 

The  line  of   contact  between  the  Albany  granite  and  an 
area  of  argillitic  mica  schist  crosses  Mount  Willard  in  the 

*  H.   Rosenbusch,  Abhandlungen   zur   geologischen    Special    Karte   von 
Elsass-Lothringen,  Bd.  I,  Heft  II,  p.  89. 


Of  THE 

UNIVERSITY 


THE  ALBANY  GRANITE.  401 

Crawford  Notch.  The  normal  rocks  with  their  contact  modi- 
fications are  familiar  to  many  of  our  geologists.  The  beauty 
of  the  natural  scenery,  combined  with  the  geological  interest, 
has  attracted  many  to  this  spot,  and  these  rocks  have  accord- 
ingly had  frequent  mention.  For  the  opinions  in  regard  to 
the  nature  and  origin  of  the  granites  at  this  point,  and  the 
interpretation  of  the  effects  that  are  due  to  the  contact,  I  refer 
to  the  second  volume  of  the  Report  on  the  Geology  of  New 
Hampshire,  by  Professor  C.  H.  Hitchcock.  As  the  relation 
of  these  peculiar  rocks  to  one  another,  and  the  nature  of  the 
changes  that  they  have  undergone  can,  however,  be  discovered 
only  by  chemical  and  microscopical  study,  it  is  neither  necessary 
nor  just  to  submit  to  critical  consideration  the  opinions  formed 
without  the  aid  of  these  methods. 

Although  Mount  Willard  is  but  a  small  mountain,  several 
of  the  most  characteristic  New  Hampshire  granites  take  part 
in  its  composition.  In  this  paper  it  is  proposed  to  confine  the 
attention  to  the  Albany  granite,*  which  forms  an  immense 
mass  covering  many  square  miles  to  the  west,  but  which 
crosses  Mount  Willard  in  the  form  of  a  dike  about  three 
hundred  feet  wide.  The  Conway  granite,  a  coarse-grained 
biotite  granite,  forms  the  hanging  wall,  and  argillitic  mica 
schists  form  the  foot  wall  of  this  dike.  Mount  Willard 
presents  a  bold  cliff  nearly  a  thousand  feet  high  toward  the 
south,  and  the  contact  lines  of  these  three  rocks  run  diag- 
onally across  this  cliff,  exposing  themselves  most  favorably 
for  study  and  observation.  We  have  here,  then,  a  small  and 
narrow  granitic  mass  which  is  connected  with  a  great  mass, 
and  this  forms  in  a  modified  way  a  parallel  to  the  celebrated 
"  Bodegang,"  which  is  a  small  narrow  dike  that  connects  the 
Ramberg  and  Brocken,  two  granite  mountains  in  the  Harz, 
the  phenomena  connected  with  which  have  been  described  by 
Lossen.f 

The  Albany  granite   is   a   very  distinctly  and    definitely 

*  So  named  by  Professor  Hitchcock  on  account  of  its  extensive  develop- 
ment in  Albany,  N.  H. 

t  Zeitschr.  d.  d.  Geol.  Ges.,  1874,  p.  856. 

26 


402  THE  ALBANY  GRANITE 

characterized  rock.  It  is  called  by  Hitchcock  the  spotted  or 
trachytic  granite.*  In  all  its  areas  it  has  the  same  peculiar 
appearance  due  to  the  development  of  Carlsbad  twins  of 
orthoclase  with  rounded  contours,  in  a  gray  fine-granular 
aggregate  of  granitic  minerals,  which  are  said  to  form  a 
mixture  resembling  pepper  and  salt.  Whether  red  or  white, 
it  is  equally  characteristic  in  appearance,  and  from  its  exten- 
sive development  it  is  to  be  considered  as  one  of  the  important 
granitic  masses  of  New  England. 

Nor  in  its  microscopic  characters  is  this  granite  less  charac- 
teristic. Its  twin  crystals  of  feldspar  in  polarized  light  are 
seen  to  have  the  peculiar  structure  of  perthite,  and  consist  of 
interlaminated  orthoclase  and  albite.f  Individual  grains  of  a 
triclinic  feldspar  are  often  seen.  The  quartz  is  in  formless 
grains  and  possesses  the  usual  fluidal  inclusions,  and  the 
position  in  angular  corners  due  to  the  order  of  crystallization. 
The  chief  accessory  is  hornblende,  which  is  black  in  the  rock, 
but  green,  yellow,  dichroic,  in  thin  sections,  and  peculiarly 
impure  from  the  inclosure  of  quartz  grains.  Biotite,  mag- 
netite, and  apatite  are  constant,  augite  and  fluor  spar  are 
frequent,  constituents. 

But  what  gives  to  this  rock  a  very  marked  microscopic 
individuality  is  the  uniform  presence  in  it  of  well-crystallized 
square  prisms  of  zircon.  Of  the  many  sections  that  have 
been  cut,  not  one  has  been  found  free  from  these  pretty 
crystals.  They  are  large  enough  to  be  examined  optically 
under  the  microscope,  and  are  easily  recognized  by  their 
tetragonal  crystallization  and  their  high  index  of  refraction. 
Their  uniaxial  and  positive  character  can  be  easily  determined 
in  convergent  light.  Out  of  twenty-five  grams  of  the  rock 
from  Mount  Willard,  I  separated  several  hundred  of  these 

*  For  distribution  of  this  granite  see  Hitchcock's  Geol.  New  Hampshire, 
vol.  ii,  p.  143. 

t  Sections  parallel  to  the  base  hardly  show  these  interlaminations  owing 
to  the  approach  in  the  elasticity  planes  of  the  two  species.  Sections  parallel 
to  the  clinopinacoid  possess  an  elasticity  plane  making  an  angle  of  6°  with 
the  basal  cleavage,  and  in  the  interlaminations  an  elasticity  plane  makes  an 
angle  of  17°  in  the  same  direction  with  the  basal  cleavage. 


AND  ITS   CONTACT  PHENOMENA.  403 

crystals  by  means  of  hydrofluoric  acid.  They  are  white, 
clear,  and  glassy,  but  are  sometimes  tinged  with  yellow. 
They  are  often  1-10  mm.  in  diameter  and  4-10  mm.  long. 
Their  surfaces  are  bright,  but  cavities  often  penetrate  far  into 
their  interiors.  They  are  doubly  terminated,  and,  in  addition 
to  the  planes  of  the  prism  and  pyramid  of  the  first  order,  they 
frequently  have  the  planes  of  a  ditetragonal  pyramid  which 
is  probably  the  form  3-3.  They  contain  many  inclusions. 
Some  of  these  are  the  inverted  forms  of  zircon  crystals,  some 
are  zircons  with  different  terminal  faces,  and  some  are  empty 
cavities  with  very  irregular  forms. 

In  the  middle  of  the  arm  of  Albany  granite  which  extends 
across  the  summit  of  Mount  Willard,  the  rock  is  of  this  normal 
character,  but  both  to  the  right  and  the  left  differences  are 
evident.  These  differences  are  of  the  same  character  upon 
both  sides,  but  they  are  very  much  more  marked  upon  the 
side  of  the  schist.  At  a  distance  of  100  feet  from  the  contact, 
the  crystals  that  form  the  granite  have  become  smaller  with 
the  exception  of  the  large  feldspar  crystals,  which  are  in 
consequence  more  conspicuous.  At  a  distance  of  sixty  feet  a 
tendency  in  the  quartz  to  assume  crystalline  forms  is  noticed, 
and  the  rock  begins  to  appear  porphyritic.  At  fifteen  feet 
from  the  contact  with  the  schists,  the  quartz  is  found  in 
well-defined  dihexagonal  pyramids,  as  large  as  peas,  and  these 
with  the  Carlsbad  twins  of  orthoclase  are  imbedded  in  a 
ground  mass  no  longer  resolvable  by  the  unaided  eye  or  lens. 
Upon  the  contact  the  ground-mass  is  nearly  black  in  color, 
flinty  in  texture,  and  apparently  homogeneous.  The  Albany 
granite  has  become  a  quartz  porphyry.* 

*  The  Bodegang  previously  referred  to  is  filled  with  quartz  porphyry 
which,  however,  has  a  coarser  ground-mass  in  the  center. 

In  the  Vosges  the  granites  which  have  altered  the  slates  are  upon  their 
side  usually  unaffected.  At  one  spot,  however,  in  the  Weihermattenthal  the 
granite  becomes  porphyritic  upon  the  contact.  Rosenbusch,  Die  Steiger 
Schiefer  und  ihre  Contactzone  an  den  Granititen  von  Barr-andlau  und 
Hohwald,  p.  156. 

In  the  Pyrenees  near  Case  de  Brousette  a  contact  occurs  between  clay 
slate  and  a  porphyry  which  farther  south  gradually  changes  into  granite. 
Zirkel,  Zeitschr.  d.  d.  Geol.  Ges.,  1867,  p.  106. 


404  THE  ALBANY  GRANITE 

The  accompanying  microscopic  changes  are  as  striking. 
Approaching  the  contact  there  is  a  continual  diminution  in 
the  amount  of  the  hornblende  and  the  size  of  its  crystals. 
There  is  a  corresponding  increase  in  the  amount  of  the  biotite, 
which  finally  entirely  replaces  the  hornblende.  These  biotite 
crystals  are  at  first  quite  large,  but  they  diminish  rapidly  in 
size  near  the  contact,  and  upon  the  contact  are  reduced  to  a 
dust.  The  ground-mass  which  makes  its  appearance  between 
the  quartz  and  orthoclase  crystals,  grows  finer,  but  upon 
the  contact,  though  of  extreme  fineness,  it  is  still  entirely 
crystalline.  In  this  ground-mass  all  the  minerals  of  the 
granite  found  in  specimens  distant  from  the  contact  are  rec- 
ognizable, but  near  the  contact  no  individual  crystals  can  be 
determined. 

In  this  series  of  changes  all  the  minerals  have  taken  part 
with  two  exceptions.  The  Carlsbad  orthoclase  twin  crystals 
and  the  zircon  crystals  have  the  same  shape  and  size  in  all 
parts  of  the  rock.  That  is,  with  these  exceptions  the  condi- 
tion or  existence  of  the  mineral  components  depends  upon 
position  with  reference  to  the  contact. 

These  modifications,  which  are  repeated  in  a  less  conspicu- 
ous manner  upon  approaching  the  contact  with  the  granite 
upon  the  opposite  side  of  the  mass,  are  such  as  might  be 
induced  in  a  molten  eruptive  mass,  which,  like  modern  lavas, 
contained  some  crystals  already  formed  at  the  time  of  erup- 
tion by  the  effect  of  contact  with  cold  walls,  the  hydrous 
nature  of  one  and  the  anhydrous  nature  of  the  other  being 
factors  modifying  the  extent  of  the  effect. 

Any  chemical  changes  that  may  be  connected  with  these 
modifications  are  represented  in  the  following  table  of  analyses. 

Of  the  differences  here  shown  some  fall  within  the  evident 
errors  of  the  analyses;  and  so  many  of  the  others  can  be 
referred  to  differences  introduced  in  sampling  such  coarse- 
grained compounds,  that  I  do  not  think  that  any  changes 
can  be  definitely  referred  to  the  effect  of  contact,  unless  it 
be  the  accession  of  iron,  and  the  slight  hydra ti on.  If  we 
assume  that  no  chemical  change  has  taken  place,  and  that 


AND  ITS   CONTACT  PHENOMENA.  405 

Normal  Albany  Granite  porphyry  Granite  porphyry 

granite.  3  ft.  from  contact.  2  in.  from  contact. 

Si02  .....  72.26  73.09  71.07 

A12O8   ....  13.59  12.76  12.34 

Fe203  ....     1.16  1.07  '  2.25 

FeO  .....     2.18  4.28  4.92 

MnO    ....      tr.  0.08  tr. 

CaO  .....     1.13  0.30  0.55 

MgO    ....     0.06  0.09  0.19 

K20  .....    5.58  5.10  5.53 

Na2O   ....     3.85  3.16  2.84 

Ti02  .....     0.45  0.40  0.27 

H20    .  .  .  .  .  0.47  0.73  0.72 

100.73  101.06  100.68 

Sp.  gr  .....  2.65  2.66  2.68 

the  first  analysis  represents  the  whole,  a  calculation  shows 
that  it  may  contain  :  — 


Quartz.      Orthoclase.      Albite.     Anorthite.  Hornblende.  Biotite.    Magnetite. 

25.99      32.95      32.61      1.35       4.83       .  .  .       1.68      0.85 
Or,  26.79      30.76      31.01      5.65       .  .  .       5.44       .  .  .      0.85 

The  biotite  has  the  composition  (K,Na)2(Fe,Mg)4AlSi4O16 
(—  one  molecule  K  and  one  M  of  Tschermak)  and  the  horn- 
blende will  be  ll(RSiO3)  +  A12O3.  This  calculation  cannot 
claim  to  be  accurate  since  there  are  no  data  for  dividing  the 
lime  between  the  anorthite  (which  is  supposed  to  be  com- 
bined with  some  of  the  albite  to  make  a  triclinic  feldspar) 
and  the  hornblende.  It  is  introduced  to  show  that  the 
results  of  the  chemical  investigation  do  not  at  all  contradict 
the  microscopic  results,  since  a  recrystallization  and  a  rear- 
rangement in  the  proportions  between  the  feldspars  furnishes 
all  the  material  necessary  to  convert  the  hornblende  into 
biotite. 

The  schists  that  occupy  the  area  indicated  upon  the  map 
form  portions  of  Mts.  Tom,  Field,  Willey,  and  Willard, 
elevations  in  the  vicinity  of  the  White  Mountain  Notch. 
Their  age  is  unknown.  Their  reference  to  the  Silurian  on 
account  of  a  supposed  fossiliferous  character  being  based 


406  THE  ALBANY  GRANITE 

upon  an  error,  it  is  only  certain  that  they  are  older  than 
both  the  Albany  and  the  Con  way  granites,  both  of  which 
intersect  them.  In  composition  they  are  not  at  all  constant, 
but  the  prevailing  variety  is  a  dark  compact  argillitic  mica 
schist  with  andalusite  crystals  scattered  through  parts  of  it. 
Upon  the  summit  of  Mt.  Willard  they  appear  to  be  very 
uniform  over  a  large  area,  and  for  this  reason  the  specimens 
for  chemical  study  were  taken  from  this  spot. 

The  schists  at  the  summit  have  a  strike  very  nearly  north 
and  south,  and  they  dip  60°  to  the  west.*  The  line  of  con- 
tact with  the  granite  runs  in  an  irregular  northwest  direction. 
At  a  distance  of  one  hundred  feet  from  this  contact,  with 
the  exception  of  the  rather  rare  andalusite  crystals,  no  min- 
erals are  visible  in  this  schist  to  the  unaided  eye,  unless  the 
glistening  surface  be  considered  as  an  indication  of  mica. 
Under  the  microscope  it  is  seen  to  consist  of  quartz,  mus- 
covite  (probably  the  variety  containing  combined  water)  and 
chlorite.  Titanic  iron  partially  decomposed  into  leucoxene, 
some  magnetic  iron  which  can  be  drawn  from  the  powder 
with  a  magnet,  and  particles  resembling  coal  or  graphite, 
constitute  opaque  black  ingredients.  A  little  biotite  and  a 
very  few  crystals  of  tourmaline,  recognized  by  form  and  the 
direction  of  strong  absorption,  are  accessory  constituents. 
No  marked  change  is  visible  in  the  rock  at  a  distance  of 
fifty  feet  from  the  contact,  but  nearer  than  this  point  the 
effect  of  the  contact  becomes  very  soon  evident.  As  the 
specimens  described  and  analyzed  were  all,  with  the  excep- 
tion of  the  normal  schist  at  one  hundred  feet,  taken  from  the 
same  stratum,  I  think  that  all  the  differences  noted  may  be 
with  certainty  regarded  as  due  to  the  effect  of  contact. 

Twenty-five  feet  from  the  contact  the  schists  are  much 
changed  in  microscopic  structure.  They  are  more  definitely 
and  coarsely  crystalline;  biotite  becomes  a  more  prominent 
constituent,  and  tourmaline  crystals,  blue  within  and  brown 
without,  have  become  a  prominent  constituent. 

*  Strike  of  slate  12°-22°  W.,  strike  of  contact  N.  77°  W.  Hitchcock's 
Geology  of  New  Hampshire,  vol.  ii,  p.  177. 


AND  ITS   CONTACT  PHENOMENA.  407 

Between  this  point  and  the  contact  the  changes  apparent 
to  the  eye  are  marked  and  rapid.  At  fifteen  feet  the  rocks 
are  still  schistose,  but  they  are  hard,  much  fractured,  and 
full  of  shining  dots  that  indicate  a  new  crystallization.  At 
this  point  the  rock  is  a  mica  schist.  Under  the  microscope, 
a  decrease  in  the  amount  of  chlorite  and  an  increase  of 
biotite  are  noted,  also  the  presence  of  many  tourmalines  and 
of  large,  clear  quartz  graius  with  fluidal  inclosures.  The 
titanic  iron  is  entirely  altered  into  a  dull  white  opaque 
substance.*  Between  this  point  and  the  contact  the  schist 
loses  entirely  its  schistose  structure,  and  is  converted  into  a 
black  hornstone,  which  breaks  into  small  angular  fragments. 
The  little  bright  crystalline  grains  of  quartz  increase  in 
quantity,  and  the  tourmalines  become  much  more  numerous. 
From  the  schists  ten  feet  from  the  contact  a  qualitative 
reaction  for  boric  acid  can  be  obtained.  The  rock,  which 
thus  far  has  been  growing  'coarser  in  texture,  from  this 
point  grows  gradually  finer,  and  is  converted  near  the  con- 
tact into  flinty,  compact  hornstone,  thin  sections  of  which 
are  resolved  by  the  microscope  into  an  aggregate  of  quartz, 
biotite,  tourmaline,  and  iron  oxide. 

But  between  this  hornstone  and  the  granite  another  well- 
defined  zone  exists.  This  is  a  dark  gray  mass  which  is  filled 
with  reticulated  black  veins.  Scarcely  noticeable  on  the 
top  of  the  mountain,  this  zone  becomes  wide  and  prominent 
below.  The  veins  which  fill  this  mass  divide  and  subdivide, 
giving  to  the  whole  a  fused,  slaggy  appearance.  Under  the 
microscope,  however,  this  mass  is  resolved  into  a  nearly  pure 
mixture  of  tourmaline  and  quartz.  While  in  the  hornstone 
zone  last  described,  the  tourmalines  are  in  extremely  minute 
formless  grains,  here  they  are  in  more  or  less  well-defined 
crystals,  and  possess  a  concentrically-banded  structure. 
White,  blue,  light  brown  and  dark  brown  layers  follow  one 

*  I  cannot  regard  the  conclusion  of  Prof.  v.  Lasaulx  that  this  substance 
is  titanite  of  lime,  titanomorphite,  as  certainly  correct  in  all  cases,  for  in 
rocks  like  this  that  are  nearly  free  from  lime  the  same  decomposition  takes 
place.  In  this  case  there  is  not  enough  lime  in  the  whole  rock  to  make 
titanomorphite  with  the  titanic  acid. 


408 


THE  ALBANY  GRANITE 


another  in  the  order  named.  These  crystals  are  bounded  by 
the  planes  —  ^  R  . ^  i  2.  This  mass  I  characterize  as  the 

zone  of  the  tourmaline  veinstone  to  distinguish  it  from  the 
last,  or  the  zone  of  the  tourmaline  hornstone.  There  is 
reason  for  this  in  the  circumstance  that  the  impregnating 
material  has  wholly  altered  the  character  of  the  schist. 

The  chemical  changes  that  have  taken  place,  both  in  ulti- 
mate composition  and  mineral  constituents,  are  indicated  in 
the  following  table  of  analyses :  — 


Si02  .  .  .  . 

Schist 
100  ft.  from 
contact. 

.  .  .   61.57 

Schist 
50  ft.  from 
contact. 

6335 

Schist 
15  ft.  from 
contact. 

66.30 

Tourmaline 
Hornstone 
1  ft  from 
contact. 

6788 

Tourmaline 
Veinstone 
on  contact. 

6641 

ALO, 

.  .  .   20.55 

1969 

1635 

1467 

1684 

Fe203   .  .  . 

.  .  .     2.02 

072 

095 

237 

1  97 

FeO      .      . 

.  .     428 

548 

577 

395 

5  nO 

MnO    .      . 

010 

016 

tr 

0  11 

0  12 

CaO  .  .  .  . 

MgO  . 

.  .  .     0.24 
.  .  .      1.27 

tr. 

1  77 

0.24 
1  63 

0.30 
129 

0.37 
1  71 

K20  .... 

.  .  .     4.71 

347 

340 

408 

0  56 

Na2O 

.     068 

1  12 

1  11 

3  64 

1  76 

Ti02 

1  10 

1  00 

1  28 

0  93 

1  02 

B00,  . 

tr. 

097 

2  96 

Fl  

tr 

025 

H20  .... 

.  .  .     4.09 

373 

302 

1  01 

1  31 

Sp.  gr.  . 

100.61 

2.85 

100.49 
2.84 

100.05 
2.82 

101.20 
2.74 

100.78 
2.73 

Quartz 36.87  39.17 

Muscovite     .  .  .   49.30  44.53 

Biotite ... 

Chlorite 8.62  13.70 

Titanic  iron    .  .      2.09  1.90 

Magnetite    .  .  .     2.93  1.04 

Tourmaline ... 

Excess  of  H00  .     0.80  0.15 


45.15 
43.89 

6.65 
2.43 
1.38 


0.55 


50.82 
29.67 

1.77 

3.44 

14.92 

0.58 


50.03 


1.94 

2.86 
45.95 


100.61        100.49        100.05        10120        100.78 


AND  ITS   CONTACT  PHENOMENA.  409 

In  these  analyses  a  systematic  and  progressive  series  of 
changes  indicates  that  there  has  been  an  addition  to  the 
schists  by  reason  of  contact  with  the  granite.  The  dehydra- 
tion and  the  accession  of  boric  and  silicic  acids  are  positive 
features,  and  the  addition  of  alkali  directly  upon  the  contact, 
in  consideration  of  the  circumstances  that  the  second,  third, 
and  fourth  samples  were  taken  from  the  same  stratum,  may 
be  regarded  as  certain  also.  The  series  of  analyses  given 
by  Professor  Rosenbusch  in  his  work  upon  the  contact  phe- 
nomena in  the  Vosges  *  prove,  in  his  opinion,  that,  whatever 
may  have  been  the  physical  changes,  nothing  (except  in  one 
case  a  little  boric  acid)  has  been  added  to  the  schists,  and  the 
analytical  results  obtained  by  others  from  contact  schists  lead 
to  the  same  result.  The  kind  of  changes  indicated  by  my 
analyses,  if  of  less  degree,  are  of  the  same  kind  as  those  that 
have  been  observed  in  the  contact  of  granites  with  lime- 
stones, as  for  example  in  the  Harz,  where  the  limestones 
about  the  Ramberg  |  have  their  CO2  replaced  by  SiO2,  form- 
ing a  broad  zone  of  lime  silicates  about  the  contact ;  and  on 
the  contact  of  limestone  with  Monzonit  f  at  Predazzo,  where 
a  similar  lime -silicate  hornstone  zone  is  found  to  be  rich  in 
alkali  directly  upon  the  contact. 

The  effect  of  the  contact  becomes  much  more  striking 
when  the  percentages  of  the  constituent  minerals  are  calcu- 
lated from  the  analyses.  This  was  done  in  the  first  two 
analyses,  as  follows.  The  titanium  dioxide  was  first  reck- 
oned into  titanic  iron,  and  the  iron  sesquioxide  calculated 
into  magnetite,  since  the  magnet  attracts  black  particles  from 
the  powder.  The  remaining  iron  protoxide,  with  the  man- 
ganese oxide,  and  the  magnesia  were  then  calculated  into  a 
chlorite  of  the  formula  of  ripidolite  (Mg5Al2Si3O14  -t-  4H2O). 
Then  if  the  remainder  of  the  alumina  is  calculated  into 
muscovite  (K,H)2  Al2Si2O8,  nothing  at  all  is  left  save  the 
small  percentages  of  water  indicated  in  the  table,  which  are 

*  Die  Steiger  Schiefer  und  ihre  Contactzone.     Strassburg,  1877,  p.  257. 
t  Lessen,  Zeitschr.  d.  d.  Geol.  Gesellschaft,  xxiv,  p.  777. 
|  J.  Lemberg,  Zeitschr.  d.  d.  Geol.  Gesellschaft,  xxiv,  p.  234 


410  THE  ALBANY  GRANITE 

not  much  more  than  what  may  be  supposed  to  be  hygroscopic, 
or  included.  In  the  third  analysis,  the  protoxides,  before 
calculated  as  belonging  wholly  to  chlorite,  have  been  divided 
equally  between  chlorite  and  biotite  in  accordance  with  the 
microscopic  indication.  The  tourmaline  hornstone  is  a  nearly 
pure  mixture  of  tourmaline  and  quartz,  as  shown  by  the 
microscope,  hence  in  the  last  analysis,  after  calculating  the 
amount  of  titanic  iron  and  magnetite,  the  remaining  bases 
were  calculated  as  forming  a  tourmaline  of  the  formula. 


wR3SiO5.       In  accordance  with   this   the  composition  of 


the  tourmaline  is  as  follows  : 

Si02        A1208      FeO      MnO     CaO     MgO     K2O     Na-jO     H20     B2O8        Fl 

35.65    36.66    8.03    0.26    0.79    3.72     1.22    3.83    2.85    6.45    0.54  =  100 

The  fourth  analysis  can  now  be  calculated  like  the  third,  after 
deducting  the  percentage  of  tourmaline  calculated  from  the 
boron  trioxide.  If  biotite  is  considered  as  a  combination  of 
the  muscovite  molecule  (K,H)2  AlSi2O8  with  the  molecule 
Mg4Si2O8  (according  to  Tschermak)  we  have  the  data  only 
for  obtaining  the  sum  of  the  muscovite  and  biotite,  but  not 
the  amount  of  each.  If  the  data  of  these  calculations  are 
not  absolutely  correct,  the  results  agree  well  with  the  micro- 
scopic observations,  and  the  table  I  think  indicates  clearly 
both  the  chemical  and  mineralogical  changes,  and  makes  it 
plain  that  they  are  progressive  in  approaching  the  granite. 

Just  between  the  schist  and  granite,  upon  the  summit  of 
the  mountain,  a  very  insignificant  zone  exists  which  consists 
of  granite  in  which  numerous  fragments  of  a  variety  of  rocks 
are  included.  This  zone,  scarcely  noticeable  upon  the  sum- 
mit, becomes  larger  and  better  denned  as  one  descends  the 
cliff,  and  I  shall  show  what  a  weighty  part  this  little  zone, 
here  but  a  foot  or  two  wide,  plays  elsewhere.  This  zone  I 
call  the  mixed  zone.  At  a  short  distance  below  the  summit 
it  becomes  a  very  sharply  defined  band  three  feet  wide,  and 


AND  ITS  CONTACT  PHENOMENA.  411 

consists  of  fragments  of  various  kinds  of  schist,  and  angular 
fragments  of  a  foreign  variety  of  quartz  porphyry,  and  all 
are  cemented  together  with  the  granitic  material.  The 
feldspar  crystals  in  this  granite  are  all  broken  to  fragments,* 
and  the  whole  mass  is  impregnated  with  tourmaline,  but  the 
constituent  minerals  are  all  easily  recognized.  The  different 
zones  that  I  have  described  are  here  all  sharply  denned.  To 
recapitulate,  these  zones  are  as  follows :  — 

1.  Zone  of  the  argillitic  mica  schist  (chloritic). 

2.  Zone  of  the  mica  schist  (biotitic). 

3.  Zone  of  the  tourmaline  horns  tone. 

4.  Zone  of  the  tourmaline  veinstone. 

5.  Zone  of  the  mixed  schists  and  granite. 

6.  Zone  of  the  granite  porphyry  (biotitic). 

7.  Zone  of  the  granite  (hornblendic). 

It  will  thus  be  seen  that  the  succession  of  zones  is  different 
from  those  that  have  been  described  about  other  granitic 
masses,  but  that  the  effects  observed  are  of  the  same  nature 
and  referable  to  the  same  causes,  f 

Following  the  line  of  contact  down  the  cliff,  the  phe- 
nomena of  the  contact  ever  becomes  more  extensive  and 
remarkable.  At  a  point  just  above  the  spot  figured,  a  long 
arm  of  the  porphyritic  granite,  from  two  to  three  feet  wide 
and  eighty  feet  long,  extends  into  the  schist  at  nearly  a  right 
angle  to  its  stratification.  The  impregnation  of  the  schists 
with  tourmaline  has  been  much  more  effectual  below  than 
upon  the  summit.  Two  hundred  feet  below  the  summit  the 
schists  distant  one  hundred  feet  from  the  contact  contain  as 
many  tourmalines  as  at  fifteen  feet  from  the  contact  upon 
the  top.  The  mixed  zone  steadily  increases  in  width  as  it 
descends,  and  at  the  base  of  the  huge  cliff  it  is  more  than 
twenty  feet  wide. 

*  The  crystals  of  orthoclase  found  in  the  small  branches  of  granitic 
masses  where  they  would  be  subjected  to  friction  have  been  often  found 
broken.  In  the  Fichtelgebirge  and  Elba  for  example.  Credner  Geologic, 
p.  285. 

t  The  zones  in  the  Vosges  as  described  by  Rosenbusch  are  :  1.  Clay  slate  ; 
2.  Knotty  clay  slate ;  3.  Knotty  mica  schist ;  4.  Hornstone,  usually  andalusite 
hornstone.  The  knotty  character  is  here  entirely  absent. 


412  THE  ALBANY  GRANITE 

These  are  the  main  features  of  this  remarkable  contact. 
I  think  they  show  that  the  Albany  granite  is  an  eruptive 
mass  younger  than  the  Conway  granite,  and  younger  than 
the  andalusite  schists,  and  that  the  main  portion  of  its  mass 
had  not  crystallized  at  the  time  of  eruption.  The  inclusion 
of  such  varied  products  in  the  mixed  zone  indicates  that  it 
moved  no  inconsiderable  distance  through  fissures  in  very 
diverse  rocks.  The  kind  of  impregnation  indicates  that  it  was 
accomplished  by  vapors  and  solutions  that  emanated  from  the 
fissures  filled  by  the  granite ;  but  the  impregnation  of  schists 
imbedded  in  the  granite,  and  the  impregnation  of  the  schists 
attendant  with  a  dehydration  of  the  same,  indicates  the  action 
of  very  hot  vapors  which  accompanied  the  eruption ;  not  the 
action  of  vapors  subsequently  emanating  through  the  cleft.* 

The  line  of  division  forming  the  contact  is  microscopically 
fine.  Over  this  line  the  minerals  of  schist  or  granite  do  not 
pass  except  in  the  form  of  inclusions.  There  is  therefore  no 
relationship  between  the  schist  and  the  granite. 

These  results  are  of  importance  in  White  Mountain  geology 
since  the  effects  are  often  repeated.  All  about  this  area,  and 
other  areas  of  Albany  granite  as  far  as  observed,  the  effects 
of  the  contact  are  found  upon  the  edges  of  the  granite.  At 
Bemis  Brook  the  same  apparent  effects  are  seen  on  the  side 
of  the  granite,  but  the  schists,  which  are  hard  siliceous  mica 
schists,  have  not  been  affected.  The  porphyry  which  at  this 
spot  adjoins  the  schist  has  the  granophyre  f  structure.  This 
structure  may  therefore  be  induced  as  a  contact  phenomenon. 

*  In  the  Vosges  andalusite  is  the  mineral  characteristic  of  the  contact,  and 
the  question  having  been  raised  whether  andalusite  ever  occurs  save  as  a  con- 
tact mineral,  this  has  been  considered.  The  apparently  systemless  method  of 
distribution  of  andalusite  crystals  over  the  whole  area  gives  no  basis  for 
referring  these  macled  crystals  to  the  effect  of  contact. 

The  cavities  in  the  quartz  of  the  granite  contain  most  variable  amounts  of 
fluid.  Some  are  full  and  some  are  empty.  The  calculation  of  temperatures 
and  pressures  upon  measured  size  of  bubble  and  cavity  can  be  of  little  value 
when,  as  is  here  plain,  other  unknown  quantities  beside  those  commonly  con- 
sidered are  factors. 

t  Used  in  the  sense  of  Rosenbusch.  That  is,  the  quartz  and  feldspar  of 
the  ground-mass  are  arranged  with  reference  to  one  another,  as  in  graphic 
granite. 


AND  ITS   CONTACT  PHENOMENA.  413 

Ascending  Mt.  Kearsarge  by  the  bridle  path  from  the 
Intervale  station,  the  base  of  the  mountain  is  seen  to  be 
composed  of  Conway  granite.*  At  a  height  of  five  hundred 
feet  one  finds  the  peculiar  gray  porphyry  with  Carlsbad  twins 
of  orthoclase  and  dihexagonal  pyramids  of  quartz,  as  on 
Mt.  Willard,  and  which  we  recognize  as  the  zone  of  the 
quartz  porphyry,  which  gradually  changes  and  finally  be- 
comes typical  Albany  granite.  Here  again  we  see  that  the 
Conway  granite  was  a  cool  body  influencing  the  crystalliza- 
tion of  a  later  eruption.  After  climbing  for  a  short  while 
over  the  Albany  granite,  the  zone  of  porphyry  again  appears ; 
then  follows  in  proper  sequence  the  mixed  zone,  but  this 
zone  which  upon  Mt.  Willard  attains  to  a  width  of  twenty 
feet  here  forms  the  whole  grand  mass  of  Kearsarge,  Bartlett 
and  Moat  Mountains.  These  mountains  from  base  to  summit 
consist  of  angular  pieces  of  schists  intermingled  with  and 
cemented  by  granite  porphyry.  The  schists  have  been  modi- 
fied by  the  contact,  but  to  a  less  degree,  since  there  has  been 
here  no  impregnation  with  tourmaline.  The  mixed  mass 
adjacent  to  the  schists  consists  of  a  very  large  amount  of 
broken  schist,  cemented  by  a  small  amount  of  the  granite, 
which  has  been  accordingly  much  modified  by  the  effect  of 
the  schist,  and  has  a  ground-mass  very  fine  in  texture,  and 
homogeneous  and  flinty  in  appearance.  Above,  where  there 
is  a  smaller  proportion  of  schist  in  the  porphyry,  this  ground- 
mass  becomes  more  coarsely  crystalline,  and  approaches 
granite  in  texture.  The  microscopic  peculiarities,  however, 
remain  constant  and  the  large  iron  crystals  never  fail. 

I  have  endeavored  to  show  that  the  contact  phenomena 
connected  with  the  Albany  granite  are  very  beautifully  devel- 
oped upon  a  small  scale,  affording  thus  exceptional  facilities 
for  study  and  observation;  but  that  on  the  other  hand  they 
reach  an  unequalled  grandeur  of  proportion.  The  evidence 
previously  offered  by  others  has  not  been  decisive  in  deter- 
mining the  eruptive  or  metamorphic  origin  of  this  rock,  and 
I  point  to  the  fact  that  many  other  important  granite  masses 

*  See  also  Atlas  to  the  Report  on  New  Hampshire  Geology,  Hitchcock. 


414  THE  ALBANY  GRANITE. 

have  been  referred  to  the  one  or  the  other  of  these  groups 
upon  the  same  insufficient  evidences  of  structure  and  internal 
stratification.  From  observations  incidental  to  this  work  I 
am,  however,  quite  certain  that  the  study  of  the  contact 
phenomena  of  the  other  great  granitic  masses  in  New  Hamp- 
shire would  develop  as  many  interesting  lithological  facts, 
and  furnish  the  proper  evidence  for  a  determination  of  their 
origin. 


ON  THE  PETROGRAPHY  OF  SQUARE  BUTTE  IN 
THE  HIGHWOOD  MOUNTAINS  OF  MONTANA. 

BY  L.  V.  PIKSSON.* 

INTRODUCTORY  NOTE.  Square  Butte  is  a  rudely  circular  mass 
of  igneous  rock  resting  on  the  point  of  the  tableland  at  the  juncture 
of  the  Arrow  River  and  Shonkin  Sag  valleys  on  the  east  side  of 
the  Highwood  Mountains  of  Montana.  This  platform  consists 
of  shales  and  sandstones  of  the  Cretaceous.  The  butte  with  its 
flat  top  forms  the  most  dominant  landmark  in  this  part  of  the 
region,  and  is  visible  for  many  miles  across  the  wide  stretches 
of  level  prairie  lands  which  surround  it.  At  the  base  its  diameter 
is  about  two  miles,  at  the  top  about  one,  and  its  thickness  is 
about  fifteen  hundred  feet. 

The  lower  part  of  the  mass  consists  of  the  dark  rock  described 
as  shonkinite  in  the  following  article,  and  this  has  been  carved 
by  erosion  into  a  series  of  towers,  crags,  buttresses,  etc.,  with 
small  wooded  glens  between,  which  completely  surround  the 
lower  base  of  the  butte.  Their  number  and  complexity  is  so 
great  that  they  form  labyrinthine  mazes  all  along  the  lower 
slopes.  In  one  place  they  are  cut  by  a  band  of  white  rock  which, 
except  for  a  certain  peculiarity  mentioned  later,  appears  much 
like  a  narrow  dike.  Ascending  through  this  maze  of  rock 
monoliths  at  a  certain  height  the  dark  basic  shonkinite  is  replaced 
by  a  white  sodalite  syenite,  whose  light  color  is  in  striking 
contrast  to  the  dark  rock  below.  There  is,  however,  no  contact 
between  the  two  masses,  one  kind  of  rock  passes  within  a  short 
distance  into  the  other  by  gradual  transition  without  change  of 
grain  or  other  contact  phenomena.  The  mass,  as  a  whole,  has  a 
marked  platy  parting  parallel  to  the  general  slope,  arid  this 
passes  through  white  syenite  and  dark  shonkinite  alike  and  also 
through  the  white  band  mentioned  above  without  regard  to  their 
differences  of  composition. 

*  From  the  "  Highwood  Mountains  of  Montana,"  by  Walter  H.  Weed  and 
Louis  V.  Pirsson.  Bull,  of  the  Geol.  Soc.  of  America,  vol.  6.  pp.  389-422, 
1895. 


416  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

The  study  of  the  mass  and  its  relation  to  the  surrounding 
sediments  forces  the  conclusion  that  it  is  a  denuded  laccolith, 
and  that  the  differences  of  its  rock  types  have  been  produced 
by  differentiation  after  the  mass  was  intruded  in  the  molten 
condition. 

PETROGRAPHY  OF  SQUARE  BUTTE. 

Characteristics  and  Minerals  of  the  dark  Rock,  Megascopic 
and  Microscopic.  —  The  dark  rock  seen  at  a  distance  appears 
of  a  grayish  black  or  dark  stone  color,  like  many  basic  diorites. 
In  the  hand  specimen,  however,  it  is  found  to  be  so  coarse- 
grained that  the  distinction  between  the  dark  colored  ferro- 
magnesian  components  and  the  light  colored  feldspathic  ones 
becomes  strongly  accentuated,  the  contrast  giving  the  rock  a 
mottled  appearance. 

Thus,  by  inspection  of  the  specimen,  one  readily  distinguishes 
the  chief  components.  They  are  augite  in  well  formed,  often 
rather  slender,  idiomorphic  crystals,  of  a  greenish-black  color, 
attaining  at  times  a  length  of  one  centimeter,  but  not  aver- 
aging perhaps  more  than  a  quarter  of  that  length,  and  biotite, 
of  a  bronzy-brown  color,  whose  occasional  cleavage  surfaces 
attain  a  breadth  of  from  one  to  two  centimeters,  but  whose 
outlines  are  not  clear  and  idiomorphic,  but  irregular,  dying 
away  among  the  other  components  in  shapeless  patches.  These 
biotites  are,  moreover,  extremely  poikilitic,  inclosing  the  other 
components.  With  the  lens  these  broad  cleavages  are  seen 
to  be  made  up  of  great  numbers  of  smaller  biotite  individuals 
in  parallel  growths,  but  including  the  other  minerals.  They 
are  thus,  as  one  might  say,  spongy,  skeleton  crystals  on  a 
large  scale. 

Filling  the  interspaces  between  these  dark  minerals  is  a 
white  feldspathic  material,  from  which  one  obtains  occasion- 
ally the  reflection  of  a  good  feldspar  cleavage.  With  the 
lens  one  detects  greenish  grains  of  olivine  in  addition. 

An  inspection  of  the  rock  shows  at  once  that  its  predominant 
character  is  the  great  abundance  of  the  augite,  which  must 
form  at  least  one-half  of  the  mass  by  volume  and  a  greater 


THE  HIGHWOOD  MOUNTAINS  OF  MONTANA.       417 

proportion  by  weight.  With  this  large  amount  of  augite,  it 
is  clear  that  if  it  were  a  dense  fine-grained  rock,  instead  of 
being  so  coarse-grained  as  it  actually  is,  a  pronounced  basaltic 
appearance  would  characterize  it. 

In  texture  the  rock  is  rather  friable  and  crumbly,  and  blows 
of  the  hammer  will  frequently  cause  a  specimen  to  fall  into  a 
coarse  gravel.  This  is  not  due  necessarily  to  alteration,  but 
to  the  great  number  of  pyroxene  prisms  and  their  idiomorphic 
character,  there  being  little  adhesion  between  their  polished 
faces  and  the  white  feldspar  material  which  fills  their  inter- 
spaces. A  single  heavy  blow  will  often  loosen  these  prisms 
so  that  the  rock  will  crumble  under  the  fingers. 

In  thin  sections  under  the  microscope  the  following  minerals 
are  found  to  be  present:  Apatite,  iron  ore,  olivine,  biotite, 
augite,  albite,  anorthoclase,  orthoclase,  sodalite,  n€phelite(?), 
cancrinite(?)  and  zeolites. 

Apatite.  —  This  is  the  oldest  mineral,  appearing  in  idiomor- 
phic outlines  even  in  or  abutting  into  the  iron  ore.  It  is  in 
short,  stout  prisms  which  often  attain  a  length  of  0.5  millime- 
ter. Though  commonly  colorless,  it  is  at  times  filled  with 
excessively  fine,  dusty  particles,  and  then  becomes  pleochroic : 
e  =  pale  steel-blue ;  CD  =  pale  leather-brown.  This  dusty 
pigment  is  very  apt  to  be  confined  to  an  inner  core,  which  is 
surrounded  by  a  clear  colorless  zone.  Sometimes  the  apatites 
are  of  a  pale  red-violet-brown  and  nonpleochroic.  The  crys- 
tals are  bounded  by  the  unit  prism  and  several  pyramids,  but 
they  were  too  small  to  determine  the  planes  on  materials 
separated  by  the  heavy  liquids.  The  basal  parting  is  common. 
Cases  of  twinning  like  that  mentioned  by  Washington  *  were 
not  observed.  As  shown  by  the  analysis,  the  mineral  is 
present  in  considerable  amount. 

Olivine.  —  This  mineral  presents  the  usual  type,  but  is  at 
times  of  a  very  pale  yellowish  color  in  the  section  and  then 
shows  a  faint  but  clearly  perceptible  pleochroism  in  tones  of 
yellow  and  white.  It  is  generally  quite  fresh,  but  sometimes 
has  borders  and  patches  of  alteration  into  a  reddish  ferru- 
ginous material. 

*  Jour.  Geol. Chicago,  vol.  viii,  1895,  p.  5. 
27 


418  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

Biotite.  —  The  large  cleavage  surfaces  of  this  mineral, 
made  up  of  composite  individuals,  have  been  described  above. 
It  is  strongly  pleochroic,  the  colors  varying  between  a  very 
pale  brownish  orange  and  a  deep  umber  brown.  Cleavage 
plates  appear  uniaxial,  but  in  the  section,  where  very  thin 
edges  may  be  found,  there  is  enough  of  an  opening  to  the 
arms  of  the  cross  in  convergent  light  to  establish  it  as 
meroxene,  the  usual  variety.  The  twinning  and  inclined 
extinction  sometimes  seen  in  the  biotites  of  nephelinite  and 
theralite  rocks  were  not  observed. 

Besides  this  brown  variety  of  biotite,  there  is  present  also 
in  much  smaller  amount  a  pure  deep  green  kind,  which, 
from  its  method  of  occurrence,  we  infer  has  been  formed 
from  the  brown  one.  All  gradations  are  found  between 
them,  but  in  such  cases  the  brown  forms  an  inner  core 
which  changes  to  green  on  the  outer  edges.  This  green  kind 
is  particularly  to  be  seen  around  the  olivines,  and  especially 
where  they  come  in  contact  with  orthoclase.  The  appear- 
ance of  these  colorless  olivines  surrounded  by  this  deep  green 
mantle  is  very  striking.  This  variety  shows  very  little 
change  of  pleochroism  or  absorption;  it  is  uniaxial,  and  its 
double  refraction  is  equally  strong  with  that  of  the  brown. 
It  is  quite  irregular  in  outline. 

The  intermediate  position  that  biotite,  in  respect  to  its 
chemical  nature,  holds  between  olivine  and  feldspar  has  been 
noted  by  Iddings  *  and  is  shown  in  the  analysis  of  its  formula. 
Thus  if  we  consider  typical  biotite  as  (HK)2(MgFe)2Al2Si3O12, 
this  separates  into  (MgFe)2SiO4  +  (HK)2O  +  A12O3"+  2  SiO2 
thus  furnishing  olivine  and  the  oxide  molecules  necessary 
for  orthoclase.  It  is  possible  that  this  intimate  relation  may 
condition  the  appearance  of  secondary  biotite  where  olivine 
and  orthoclase  are  contiguous. 

Pyroxene.  —  Of  all  the  ferro-magnesian  minerals  this  is  by 
far  the  most  important,  determining  with  the  orthoclase 
the  essential  character  of  the  rock.  Owing  to  the  ease  with 
which  it  may  be  detached  from  the  matrix,  excellent  speci- 

*  Origin  Igneous  Hocks :  Bull.  Phil.  Soc.  Washington,  vol.  xii,  1892, 
pp.  165,  166. 


THE  HIGHWOOD  MOUNTAINS   OF  MONTANA.       419 

mens  may  be  obtained  for  crystallographic  study.  In  general 
they  present  the  common  form  of  augite  bounded  by  the 
planes  a(100),  5(010),  ra(110)  and  «(Ill),  and  somewhat 
tabular  on  #(100).  The.  form  0(221)  has  also  been  observed. 
Twinning  on  a(100)  occurs,  and  a  crystal  of  this  type  hav- 
ing the  form  0(221)  in  addition  was  measured  on  the  reflect- 
ing goniometer  with  the  following  results  :  — 

Theory.        Measured. 

a  Am  (100  A  110)  46°  25'  46°  27'    46°  23'    46°  42'     46°  51' 

SA  ^(l  IT  A  ITT)  59°  11'  59°    8' 

mA  0  (110A22T)  35°  29'  35°  40' 

SA  s  (1  IT  A  Til  twin)  26°  52'  26°  24'     26°  35' 

The  reflections  of  the  signal  were  only  moderately  good, 
and  the  measured  angles  are  therefore  of  value  only  in  deter- 
mining the  faces. 

As  this  variety  of  augite  is  very  common  and  persistent, 
not  alone  at  Square  Butte  but  generally  throughout  the  High- 
wood  rocks,  at  times,  however,  passing  into  varieties  which 
have  a  narrow  mantle  of  material  rich  in  the  segirite  mole- 
cule, as,  for  example,  segirite  -augite,  it  has  been  deemed 
important  to  investigate  it  chemically,  especially  since  the 
Square  Butte  rock  presents  such  excellent  material.  The 
analysis  yielded  the  following  results  :  — 

ANALYSIS  OF  PYROXENE. 


Oxygen  ratios. 

SiO 

49.42 

0.8236)    08303 

Ti02  .  . 

0.55 

0.0067  ) 

A1203  . 

4.28 

°-0415l    0.0593 

Fe208  . 

2.86 

0.0178  i 

FeO  ,  . 

5.56 

0.0772  ) 

MnO 

0.10 

0.0014V   0.4181^ 

MgO    . 

,  ,   .      13.58 

0.3395)  (1.04) 

CaO 

,  ,  22.35 

0.3995      0.3995  ' 

(1.00) 

Na20    , 

1.04 

0.0167)    00207 

K20.  . 

0.38 

0.0040  ) 

H20  (at 

110°)     0.09 

Total 

100.21 

0.8176 


420  *         PETROGRAPHY  OF  SQUARE  BUTTE  IN 

In  the  foregoing  analysis  the  rock  was  crushed,  sifted,  and 
the  resulting  powder  washed  and  then  separated  by  the  use 
of  Retgers'  *  silver-thallium-nitrate  fluid  in  the  apparatus 
devised  by  Professor  Penfield,f  and  by  this  means,  aided  by 
the  magnet,  material  of  exceptional  purity  was  obtained. 

The  comparison  of  the  ratios  in  the  analysis  shows  that 
CaO  to  (FeMg)O  is  as  1  to  1,  and  that  the  diopside  molecule 
is  thus  chiefly  present.  The  presence  of  the  alumina  sug- 
gests that  Tschermak's  molecule  RAl2SiO6  must  also  be 
present.  If  we  subtract  from  the  sum  of  the  RO  molecules 
enough  to  make  the  number  of  the  R2O  equal  to  that  of  the 
R2O8  and  take  out  the  same  number  of  SiO2  molecules,  the 
following  table  shows  the  composition  of  the  augite  :  — 


EC?  =  °'°593  :  E°  =  °'°593  :  Si°  = 


EO   =  0.7790  :  Si02  =  0.7710  :  :  1  :  1.01. 

The  very  striking  agreement  of  these  ratios  with  the  theory 
must  certainly  be  held  to  add  another  very  strong  proof  to 
the  correctness  of  Tschermak's  assumed  molecule.  The 
augite  then  has  almost  exactly  the  following  composition: 
13Ca(MgFe)Si2O6  +  2(Na2R(AlFe)2SiO6. 

Since  the  qualitative  analysis  of  the  feldspars  has  shown 
the  absence  of  lime,  if  we  deduct  enough  from  the  amount 
found  by  the  mass  analysis  of  the  rock  to  turn  the  phosphoric 
anhydride  into  apatite,  a  comparison  of  the  remaining  amount, 
11  per  cent,  with  the  22  per  cent  of  lime  demanded  by  the 
pyroxene,  shows  this  mineral  forms  one-half  of  the  rock  by 
weight,  a  fact  which  agrees  with  the  appearance  of  the  hand 
specimen  and  the  study  of  thin-sections. 

*  Jahrbuch  fur  Min.  1893,  vol.  i,  p.  90.  This  most  happy  discovery  of 
Professor  W.  Retgers  has  placed  all  working  mineralogists  and  petrographers 
deeply  in  his  debt. 

t  We  desire  to  express  our  thanks  to  Professor  S.  L.  Penfield  for  kindly 
aid  in  making  the  separation  in  apparatus  recently  devised  by  him  for  the 
special  use  of  the  Retgers'  fluid,  and  by  means  of  which  the  operation  may  be 
carried  on  with  nearly  the  same  ease  and  with  all  the  certainty  of  the  usual 
heavy  liquids. 


THE  HIGHWOOD  MOUNTAINS  OF  MONTANA.       421 

Orthoclase.  —  The  predominant  feldspar  is  orthoclase.  This 
is  shown  by  the  study  of  thin-sections,  by  the  separation  of 
the  feldspathic  constituents  by  heavy  liquids,  and  may  also 
be  inferred  from  the  chemical  analysis  of  the  rock,  where 
potash  is  seen  to  greatly  predominate  over  soda.  The 
mineral  is  quite  fresh  and  wholly  allotriomorphic,  its  shape 
being  determined  by  the  angular  interspaces  between  the 
pyroxenes  in  which  it  is  found.  Sometimes  it  assumes  rude 
lath-shaped  forms. 

It  is  apt  to  be  filled  with  fine  interpositions  whose  exact 
nature  cannot  be  told.  They  commonly  possess  the  form  of 
their  host  and  their  longer  axis  coincides  with  that  of  the 
crystal,  and,  so  far  as  can  be  determined,  they  are  arranged 
in  planes  parallel  to  prism  faces.  They  do  not  contain 
bubbles,  the  reflection  band  surrounding  them  is  narrow  and 
they  do  not  act  on  polarized  light.  From  these  facts  we 
believe  them  to  be  of  glass. 

Sometimes  the  orthoclase  is  colored  a  pale  brownish  tone 
by  a  fine  dusty  pigment.  It  shows  in  some  places  a  slight 
tendency  to  kaolinization  and  in  some  others  is  discolored  by 
the  alteration  of  its  interpositions,  but  usually  it  is  quite 
fresh.  The  angle  of  the  optic  axes  is  variable,  generally 
small  and  sometimes  nearly  zero. 

It  sometimes  shows  intergrown  patches  of  a  feldspar  which 
has  a  higher  index  of  double  refraction  and  is  believed  to 
be  anorthoclase.  In  a  few  cases  a  tendency  for  orthoclase 
laths  to  group  themselves  in  radial  spherulitic  forms  starting 
from  a  common  centre  was  observed;  since  the  laths  are 
broad  and  coarse  it  does  not  present  a  striking  feature. 
Again,  in  other  places  the  patches  of  orthoclase  filling  adjoin- 
ing areas  between  augites  and  olivines  have  the  same  optical 
orientation  over  some  distance,  thus  presenting  a  rude  poiki- 
litic  effect. 

Plagioclase.  —  A  triclinic  striated  feldspar  is  also  present, 
but  in  no  considerable  amount.  When  the  rock  powder  is 
placed  in  the  mercuric-iodide  solution,  and  the  ferro-magne- 
sian  minerals,  the  magnetite  and  apatite  have  fallen  out,  no 


422  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

feldspathic  materials  are  deposited  until  a  specific  gravity  of 
2.60-2.61  is  reached.  At  this  point  a  very  small  precipitate 
is  obtained  of  a  feldspar  insoluble  in  HC1.  Subjected  to 
qualitative  analysis  it  is  found  to  be  free  from  lime  and 
gives  abundant  reaction  for  soda.  It  is  therefore  albite, 
which  agrees  with  the  optical  character  of  the  mineral  in 
thin-sections,  the  extinction  on  either  side  of  the  albite 
twinning  plane  reaching  a  maximum  of  about  fifteen  degrees. 
The  study  of  this  striated  feldspar  has  shown  that  certain 
crystals  possess  remarkable  properties.  Thus  the  twinning 
lamellae,  which  are  very  narrow,  can  be  seen  in  many  cases 
very  distinctly  in  ordinary  light  without  using  the  analyzer, 
some  of  them  possessing  a  higher  refraction  than  others. 
Between  crossed  nicols  it  is  seen  that  crystals  possessing 
this  peculiarity  have  no  position  of  equal  illumination,  but 
the  lamellae  can  be  seen  in  all  positions.  It  must  be,  there- 
fore, that  these  lamellae  possess  a  different  chemical  composi- 
tion from  those  adjoining  them,  and  since  lime  is  excluded 
they  must  represent  intergrowths  of  albite  and  anorthoclase 
of  varying  composition,  joined  after  this  singular  manner. 

Recently  Federoff*  has  called  attention  to  similar  inter- 
growths  of  twin  lamellae  of  different  composition  in  the 
lime-soda  feldspars,  and  the  same  phenomenon  had  been 
studied  and  noted  previously  by  Michel-Levy,  f 

NepJieline.  —  The  presence  of  this  mineral  is  only  indicated 
by  the  fact  that  the  powders  falling  between  the  specific 
gravities  of  2.55  and  2.60  dissolve  slightly  in  HC1,  giving  a 
small  amount  of  gelatinous  silica,  with  reactions  for  Na  and 
none  for  01,  H2O  or  CO2.  It  must  be  present  in  the  rock 
only  as  a  rare  accessory  mineral,  and  the  recognition  in  the 
thin-sections  of  an  occasional  patch  is  rendered  difficult  by 
the  practically  uniaxial  character  of  some  of  the  orthoclase. 

Oancrinite.  —  This  is  indicated  by  the  fact  that  the  rock 
powder  obtained  at  a  specific  gravity  of  2.47  dissolved  in 
HC1  with  gelatinization,  and  in  dissolving  slowly  and  con- 

*  Zeit.  fur  Kryst.  vol.  24,  Hefte  1  and  2,  1894,  p.  130. 
I  Mineraux  des  Roches  :  Paris,  1888,  p.  84. 


THE  HIGHWOOD  MOUNTAINS  OF  MONTANA.       423 

tinuously  gave  off  CO2,  while  carbonates,  which  would  have 
been  thrown  down  at  a  higher  specific  gravity,  are  absent  in 
the  rock,  as  seen  in  thin-sections.  It  can  be  present  only  in 
very  small  amount,  and  the  certainty  of  recognizing  an 
occasional  piece  in  the  section  is  diminished  by  the  common 
occurrence  of  natrolite.  The  two  minerals  are  alike  in  their 
appearance  in  fibres  with  parallel  extinction.  The  cancrinite 
has,  it  is  true,  a  higher  double  refraction,  but  sections  may 
be  as  low  as  natrolite,  and  only  by  establishing  the  uniaxial 
character  can  the  cancrinite  be  definitely  determined.  This 
we  have  not  been  able  to  do,  and  its  presence  is  therefore 
only  inferential. 

Sodalite.  —  This  also  occurs  as  an  accessory  component. 
The  rock  powder  separated  below  a  specific  gravity  of  2.40 
consists  partly  of  this  mineral,  together  with  some  zeolites. 
It  dissolves  readily  in  HC1  and  HNO3,  the  solution  in  the 
latter  yielding  a  precipitate  with  AgNO3  and  none  with 
BaCl2,  thus  showing  the  presence  of  sodalite  and  absence  of 
hauyn  or  nosean.  In  thin-section  it  is  very  clear  and  limpid, 
but  contains  little  interpositions  somewhat  like  the  feldspars. 
The  actual  amount  of  sodalite  in  the  rock  is  very  small,  and 
this  is  shown  also  by  the  small  amount  of  chlorine  obtained 
in  the  analysis,  part  of  which  belongs  to  the  apatite  present. 

Natrolite.  —  The  presence  of  zeolites  is  indicated  by  the 
water  obtained  in  the  analysis.  Some  analcite  may  occur, 
but  the  chief  zeolite  is  natrolite,  which  is  present  in  con- 
siderable amount.  It  is  recognized  by  its  parallel  extinction 
and  positive  character,  by  the  small  angle  of  the  optic  axes, 
and  by  the  strength  of  its  double  refraction,  which  compared 
with  the  feldspars,  rises  to  0.010-0.012.  It  occurs  in  char- 
acteristic bundles  of  fibers,  and  is  in  part  secondary  after 
sodalite  and  in  part  after  albite  and  anorthoclase.  The  fibers 
are  plainly  seen  eating  their  way  into  the  feldspar,  and  in  a 
given  crystal  they  do  this  according  to  a  definite  oriented 
direction,  as  the  different  patches  in  the  crystal  always  have 
the  same  orientation. 

Chemical  Composition.  —  The  chemical  composition  of  the 


424  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

rock  is  shown  in  the  following  analysis.  In  it  the  minute 
trace  of  CO2  due  to  a  little  possible  cancrinite  is  not  deter- 
mined, nor  is  the  amount  of  rarer  elements  which  could  not 
influence  its  results.  The  very  large  amount  of  P2O5  is 
noticeable,  and  proves  what  the  microscope  reveals,  the  large 
amount  of  apatite  present.  The  amount  was  fixed  by  two 
closely  agreeing  determinations. 

ANALYSIS  OF  SHONKINITE.* 


TiO    

....    0.78 

ALO, 

....  10.05 

Fe  0Q 

....    3.53 

FeO  

....    8.20 

MnO  

.  .  .  .    028 

MgO. 

....     9.68 

CaO  

....  13.22 

JSTa  0  

....    1.81 

KO   

....    3.76 

H00  . 

....     1.24 

P.,0K  . 

....    1.51 

Cl   

....    0.18 

0  -  01    ... 

100.97 
....    0.04 

Total 100.93 

To  be  noted  here  is  the  low  silica  and  very  high  magnesia, 
iron,  and  lime.  It  is  evident  that  although  the  feldspar  raises 
the  silica  percentage  it  is  not  in  sufficient  amount  to  counter- 
act the  olivine,  iron  ore,  biotite,  apatite  and  other  minerals 
which  tend  to  lower  it.  The  water  comes  in  part  from 
zeolites. 

Structure  and  Classification.  —  The  minerals  in  the  order 
of  their  crystallization  are,  first,  apatite,  then  iron  ore, 
olivine,  biotite,  and  augite.  The  period  of  the  last  two 

*  Since  this  analysis  was  published  a  recalculation  of  the  analytical  data 
shows  an  error  in  calculating  the  MgO  which  should  be  9.25  and  the  total 
100.50. 


THE  HIGHWOOD  MOUNTAINS  OF  MONTANA.       425 

overlaps.  Then  followed  the  feldspathic  components,  whose 
succession  is  quite  doubtful  as  regarding  one  another,  except 
that  on  the  whole  the  albite-anorthoclase  group  appears  to  be 
among  the  earliest. 

These  minerals  lie  unoriented,  forming  a  hblocrystalline, 
rather  coarse  granular  hypidiomorphic  structure.  It  resembles 
in  many  respects  the  coarser  grained  theralites  of  the  Crazy 
Mountains ;  in  others  certain  coarse-grained  dolerites. 

From  what  has  been  given  in  the  foregoing  description  it 
is  evident  that  in  this  dark  rock  of  Square  Butte  we  have  a 
granular,  plutonic  rock,  composed  essentially  of  augite  and 
orthoclase,  with  smaller  amounts  of  olivine  and  iron  ore  and 
with  accessory  apatite,  sodalite,  nepheline,  et  cetera.  In  its 
chemical  composition  it  stands  very  close  to  certain  vogesites 
and  minettes  —  basic  rocks  of  the  syenitic  group.  It  differs 
from  them  essentially,  first,  in  its  mineral  composition  and, 
second,  in  its  structure.  For  a  rock  of  its  character  there 
seems  to  be  no  position  in  any  of  our  present  schemes  of 
classification.  It  would  be  manifestly  improper  to  term  such 
a  rock  an  augite-syenite,  as  its  chemical  composition  removes 
it  very  far  from  syenites.  It  bears,  indeed,  such  a  relation 
to  augite-syenite  as  vogesite  does  to  hornblende-syenite;  that 
minette  or,  perhaps,  better,  the  Durbachite  of  Sauer  *  does 
to  mica-syenite. 

It  stands  generally  related  indeed  to  rocks  of  the  basic 
class  — low  in  SiO2,  high  in  MgO,  CaO,  and  FeO,  and 
thereby  related  to  rocks  of  the  lamprophyre  family.  More- 
over, this  type  is  found  in  the  High  woods  not  only  in  the 
outer  mantle  of  Square  Butte,  although  constituting  there 
an  immense  mass,  but  at  many  other  points  forming  great 
intrusive  stocks.  As  briefly  noted  by  Lindgren,f  the  vari- 
ability of  the  augite  and  orthoclase  in  the  Highwood  rocks 
is  very  great.  As  in  the  gabbro  family  we  have  every  range 
from  anorthosite  at  one  end  to  peridotites  at  the  other,  with 

*  Mitt.  d.  Bad.  geol.  Landesanstalt,  ii.  Bd.,  p.  247. 

t  Proc.  California  Acad.  Sci.,  ser.  2,  vol.  iii,  p.  47.  Tenth  Census,  vol.  xv, 
p.  725. 


426  PETROGRAPHY  OF  SQUARE  EUTTE  IN 

the  gabbros  standing  in  an  intermediate  position,  so  in  the 
Highwoods  variation  extends  from  syenites  practically  devoid 
of  ferro-magnesian  minerals  to  those  in  which  augite  becomes 
the  chief  constituent,  though  the  basic  extreme  entirely 
devoid  of  feldspar  has  not  been  observed  by  us. 

Name  Shonkinite,  —  For  this  type  of  rock,  then,  we  pro- 
pose the  name  of  shonkinite,  from  Shonkin,  the  Indian  name 
of  the  Highwood  range,  by  which  name,  indeed,  it  is  still 
called  by  many,  and  shonkinite  we  define  as  a  granular 
plutonic  rock  consisting  of  essential  augite  and  orthoclase, 
and  thereby  related  to  the  syenite  family.  It  may  be  with 
or  without  olivine,  and  accessory  nepheline,  sodalite,  et  cet- 
era, may  be  present  in  small  quantities.  The  Square  Butte 
rock  is  thus  olivine-shonkinite,  with  these  accessor}*  minerals. 

The  fine-grained  dense  porphyritic  forms  which  bear  the 
same  relation  to  shonkinite  that  trachyte  does  to  syenite  are 
dark  to  black  heavy  basalts.  They  are,  in  fact,  orthoclase 
basalts,  a  type  which,  although  so  far  as  we  know  has  not 
yet  been  described  from  European  localities,  is  by  no  means 
rare  in  western  America.  Besides  its  occurrence  in  the 
Highwoods,  and  also  in  other  localities  in  Montana  alluded 
to  by  Lindgren,*  its  presence  in  the  Absaroka  Range  and 
Yellowstone  National  Park  has  been  mentioned  by  Iddings.f 
Somewhat  similar  rocks  have  been  also  mentioned  by  Zirkel,f 
who  does  not,  however,  discuss  this  type  of  basalts  in  the 
recent  edition  of  his  great  work  on  petrography,  so  far  as 
we  have  been  able  to  discover  in  the  absence  of  complete 
indexing. 

White  Rock  or  Sodalite-syenite.  — The  petrography  of  the 
light-colored  inner  core  of  the  denuded  laccolite  has  been  so 
completely  investigated  by  Lindgren  and  Melville  §  that  a 
further  examination  enables  us  to  add  but  very  little  to 
their  comprehensive  description.  The  rock  is  shown  to  be  a 

*  Loc.  cit.,  p.  50;  also  Am.  Jour.  Sci.,  vol.  45,  1893,  p.  289. 
t  Bull.  Phil.  Soc.  Washington,  vol.  12,  1892,  p.  169. 
}  Mic.  Petrog.  Fortieth  Par.,  1876,  p.  225. 
§  Loc.  cit. 


THE  HIGHWOOD  MOUNTAINS   OF  MONTANA.       427 

sodalite-syenite,  and  for  purposes  of  convenience  we  briefly 
summarize  their  results,  referring  to  the  original  paper  for 
fuller  information. 

Megascopically  the  rock  when  very  fresh  is  nearly  pure 
white,  often  with  a  brownish  to  pinkish  tinge,  consisting 
mainly  of  feldspar,  which  often  reaches  5  millimeters  in 
diameter.  Through  this  are  scattered  slender,  glittering 
black  hornblende  prisms  which  attain  at  times  the  same 
length.  It  is  scarcely  sufficient  in  amount  to  detract  at  a 
distance  from  the  general  whiteness  of  the  rock.  Small 
grains  of  a  salmon  to  brown  colored  sodalite  are  also  present. 
The  rock  is  thus  rather  coarsely  granular,  and,  in  fact,  of 
the  same  size  grain  as  the  shonkinite,  with  which  it  is  so 
intimately  connected. 

The  microscope  shows  the  following  minerals  present  in 
the  order  of  their  formation:  Apatite,  hornblende,  orthoclase 
(with  some  albite),  sodalite,  and  analcite.  The  hornblende 
is  in  slender  prisms  bounded  by  w,  110,  and  5,  010,  termina- 
tions wanting,  frequently  twinned  on  a(100).  It  is  strongly 
pleochroic  C  and  b,  deep  brown;  a,  yellowish  brown  and 
absorption  very  great  b  =  C  >  3-  An  outer  mantle  often 
shows  a  greenish  color  (from  change  into  the  arfvedsonite 
molecule?  —  L.  V.  P.).  Angle  c  A  c  =  13  degrees;  is  idio- 
morphic  against  the  feldspathic  constituents.  It  is  closely 
related  to  barkevikite,  as  shown  by  the  analysis  quoted  later 
in  this  article. 

The  orthoclase  occurs  in  lath-shaped  forms  and  in  irregular 
grains.  Those  abutting  against  sodalite  show  crystal  faces. 
Associated  with  the  orthoclase  is  a  triclinic  feldspar  referred 
to  albite.  The  sodalite  is  found  in  irregular  grains  between 
the  feldspars,  allotriomorphic  in  regard  to  them,  idiomorphic 
against  analcite.  The  latter,  which  is  in  considerable  amount, 
was  along  with  the  sodalite  separated  and  analyzed.  The 
analcite  is  thought  to  be  derived  from  the  albite.  The  rock 
is  calculated  from  the  analysis  (given  later  in  this  paper)  to 
consist  of  66  parts  of  feldspar,  23  of  hornblende,  8  of  sodalite 
and  3  of  analcite. 


428  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

In  addition  to  these  facts  we  have  only  to  add  that  in  the 
additional  material  studied  by  us  we  have  detected  a  small 
amount  of  nephelite,  which  is  being  changed  by  borders, 
bays,  and  tongues  of  analcite  eating  into  it  and  thus  suggest- 
ing an  additional  origin  for  the  analcite;  also  considerable 
natrolite  is  sometimes  present.  Its  fibrous  masses  are  second- 
ary after  sodalite  and  at  times  it  completely  replaces  it. 

GENERAL  PETROLOGY  OP  SQUARE  BUTTE. 

The  facts  which  have  already  been  given  in  regard  to 
Square  Butte  show  it  to  be  one  of  the  most  remarkable  and 
interesting  occurrences  of  an  igneous  rock  that  has  been 
described  and  from  a  petrologic  point  of  view  one  of  the 
most  important;  for  while  the  differentiation  of  a  molten 
magma  as  a  factor  in  the  formation  of  igneous  rocks  is  now 
regarded  by  the  majority  of  petrologists  as  an  established 
fact,  it  is  also  true  that  the  theory  has  been  founded  almost 
entirely  upon  inferential  proof  and  by  the  exclusion  of  other 
hypotheses.  The  direct  proofs  which  have  come  under  obser- 
vation have  not  been  all  that  could  be  desired,  and  some  of 
them  indeed,  as  in  the  case  of  mixed  dikes,  have  had  more 
than  one  interpretation. 

In  the  case  of  Square  Butte,  however,  the  proof  of  differ- 
entiation is  unequivocal  and  direct,  for  in  no  other  rational 
way,  we  believe,  would  it  be  possible  to  explain  the  disposi- 
tion of  the  rock  masses,  the  cone-in-cone  arrangement  of  the 
two  differing  masses  of  intruded  igneous  rock,  so  unlike  in 
chemical  and  mineral  composition,  yet  geologically  a  unit 
and  absolutely  homogeneous  in  granularity  and  texture  and 
so  perfect  in  continuity  of  structure  and  platy  parting. 

It  is  therefore  a  matter  of  interest  to  compare  the  chemical 
and  mineral  composition  of  these  two  rocks,  the  syenite  and 
shonkinite,  with  one  another,  and  see,  so  far  as  possible,  how 
and  under  what  conditions  the  differentiation  has  taken 
place.  For  this  purpose  the  analyses  of  the  two  rocks  are 
herfe  compared :  — 


THE  HIGHWOOD  MOUNTAINS   OF  MONTANA.      429 


Chief  oxides  to  100. 


Molecules. 


A 

B 

Ai 

BI 

A2 

B2 

Si02 

56.45 

46.73 

Si02 

57.83 

48.36 

65.61 

49.27 

Ti02 

0.29 

0.78 

A1208 

20.57 

10.40 

13.62 

6.27 

A1203 

20.08 

10.05 

FeO 

5.72 

11.78 

5.39 

10.02 

1.31 

3.53 

MgO 

0.64 

10.01 

1.10 

15.28 

FeO8 

4.39 

8.20 

CaO 

2.19 

13.68 

2.65 

14.84 

MnO 

0.09 

0.28 

Na20 

5.75 

1.88 

6.33 

1.82 

MgO 

0.63 

9.68 

K20 

7.30 

3.89 

5.30 

2.50 

CaO 

2.14 

13.22 

100.00 

100.00 

100.00 

100.00 

Na20 

5.61 

1.81 

K20 

7.13 

3.76 

H20 

1.77 

1.24 

P  0 

0.13 

1.51 

Cl 

0.43 

0.18 

100.45 

100.97 

0  =  C1 

0.10 

0.04 

Total 

100.35 

100.93 

In  the  above  table  the  analysis  of  the  syenite  by  Melville  is 
given  under  A ;  that  of  the  shonkinite  by  Pirsson  is  repeated 
under  B.  For  purposes  of  more  easy  comparison  they  are 
repeated  under  A1  and  B1,  with  the  non-essential  elements 
omitted,  the  ferric  iron  reduced  to  ferrous,  and  the  whole 
brought  to  100.  This  at  once  brings  out  the  most  important 
chemical  characteristics  of  the  shonkinite,  its  very  high  iron, 
lime,  and  magnesia,  properties  which  show  its  difference  from 
the  typical  syenites  and  its  approach  to  the  basaltic  and 
lamprophyre  groups.  In  A2  and  B2  are  given  the  percentages 
of  molecules  in  the  rocks  derived  from  the  oxygen  ratios. 
The  percentages  by  molecules  gives  in  general  a  much  clearer 
idea  of  the  chemical  composition  of  a  rock  than  that  by 
weight,  because  it  shows  more  correctly  its  capacity  for 
forming  minerals. 

From  the  above  table  it  is  seen  at  once  that  the  magnesia 
shows  the  greatest  differentiation,  then  the  lime,  and  then 
iron.  The  relative  proportion  of  the  alkalies  to  each  other 
and  to  alumina  is  about  the  same  in  each ;  they  vary  some- 
what, it  is  true,  but  the  variation  is  insignificant  compared  with 


430  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

that  of  the  bivalent  oxides.  The  tendency  of  variation,  then, 
has  been  for  the  lime,  iron,  and  magnesia  molecules  toward 
the  outer  cooling  surface,  while  the  alkalies  and  alumina 
have  remained  a  constant,  or  if  we  imagine  the  silica  to 
remain  a  constant,  they  have  moved  inwardly.  It  is  also 
clear  that  the  bivalent  oxides  have  riot  kept  a  nearly  constant 
ratio,  for  magnesia  is  much  more  concentrated  than  iron. 

Of  course,  this  implies  that  the  molten  mass  before  intru- 
sion into  the  laccolite  cavity  was  of  uniform  composition; 
that  one  liquid  mass  of  one  kind  was  not  succeeded  by 
another  of  different  composition.  The  very  regular  and 
symmetric  arrangements  of  the  parts,  the  absence  of  all 
inclusions  or  "schlieren,"  the  cleanness  of  the  zonal  edge, 
together  with  the  common  properties  already  pointed  out, 
utterly  preclude  this  idea.  There  are,  indeed,  places  in  the 
Highwoods  where  intruded  masses  show  further  movements 
after  differentiation  has  taken  place,  with  the  result  of 
remarkably  banded  and  streaked  rocks,  whose  very  occur- 
rence shows  that  such  was  not  the  case  at  Square  Butte. 

We  are,  indeed,  forced  to  conclude  at  every  step  that  the 
mass  was  originally  homogeneous,  and  that  differentiation 
took  place  by  the  diffusion  of  the  bivalent  oxides  toward  the 
outer  surfaces. 

It  would  add  greatly  to  the  value  of  the  results  here 
presented  if  we  could  know  or  could  obtain  the  composition 
of  the  original  magma  in  which  the  differentiation  took  place. 
This,  however,  cannot  be  done  by  comparing  the  masses  of 
the  two  rocks,  because,  although  it  is  probable  that  the 
amount  of  syenite  now  present  represents  pretty  nearly  the 
original  one  —  that  is,  that  there  has  been  only  a  small 
erosion  of  that  rock  —  the  case  is  quite  different  with  the 
shonkinite,  a  very  large  part  of  which  has  been  carried  away ; 
hence,  not  knowing  the  relation  of  the  two  masses  involved, 
we  cannot  estimate  the  composition  of  the  original  magma. 
It  is  evident,  however,  that  it  must  have  been  between  the 
syenite  and  shonkinite. 

Shonkinite,  however,  occurs  in  large  bodies  in  the  neigh- 


THE  HIGHWOOD  MOUNTAINS   OF  MONTANA.       431 

borhood  of  Square  Butte  and  elsewhere  throughout  the  High- 
wood  range,  while  rocks  closely  related  to  it  in  chemical  and 
mineral  composition  are  found  in  the  form  of  dikes,  extruded 
lavas,  and  breccias.  Throughout  the  district  what  may  be 
called  acid  or  highly  feldspathic  rocks  play  but  a  subordinate 
role.  In  view  of  these  facts,  we  are  inclined  to  believe  that 
the  composition  of  the  original  magma  approximated  more 
closely  to  shonkinite  than  to  the  syenite. 

It  will  be  seen,  therefore,  that  Square  Butte  presents  in  a 
demonstrative  way  the  same  idea  that  Brogger  inferentially 
deduced  and  presented  as  the  explanation  of  the  processes 
of  differentiation  by  which  the  varied  rocks  of  the  region  of 
South  Norway  have  been  formed.* 

Recently  Harker  f  has  described  an  interesting  occurrence 
of  a  gabbro  massif,  which  grows  steadily  more  basic  or  richer 
in  the  ferro-magnesian  minerals  as  the  outer  boundary  is 
approached.  Harker  explains  this  occurrence  by  pointing 
out  that  the  order  of  concentration  of  the  minerals  is  the 
same  as  the  order  of  their  crystallization,  and  hence  accounts 
for  the  differentiation  as  a  process  of  crystallization.  Square 
Butte  is  also  more  basic  as  we  approach  the  outer  boundary, 
but  the  transition  occurs  abruptly,  so  to  speak,  or  within 
such  a  narrow  zone  that  it  practically  does.  It  is  evident, 
however,  that  differentiation  did  not  take  place  at  Square 
Butte  as  a  process  of  crystallization,  but  in  a  liquid  magma 
before  any  crystallization  occurred.  This  is  rendered  quite 
evident,  since  none  of  the  ferro-magnesian  minerals  of  the 
shonkinite  are  found  in  the  syenite.  The  only  one,  indeed, 
which  is  found  in  the  syenite  is  the  barkevikite-like  horn- 
blende, while  in  the  shonkinite  are  found  iron  ore,  biotite, 
olivine,  and  pyroxene.  Thus  Square  Butte  affords  a  striking 
confirmation  of  the  ideas  recently  expressed  by  Brb'gger  in 
his  remarkable  work  on  the  basic  rocks  of  Gran.  J 

It  is  a  matter  of  some  interest  here  to  compare  the  com- 

*  Zeit.  fur  Kryst,  vol.  xvi,  1890,  p.  85. 

t  Quart.  Jour.  Geol.  Soc.,  vol.  1,  1894,  p.  311. 

t  Quart.  Jour.  Geol.  Soc.,  vol.  1,  1894,  p.  15. 


432  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

position  of  the  augite  of  the  shonkinite,  by  far  its  most 
prominent  constituent,  and  the  hornblende  of  the  syenite 
from  Melville's  analysis. 

Barkevikite.        Augite. 

Si02 38.41  49.42 

Ti02 1.26  0.55 

A1208 16.39  4.28 

Fe203 3.75  2.86 

FeO 21.75  5.56 

MnO 0.15  0.10 

MgO 2.54  13.58 

CaO 10.52  22.35 

Na20 2.95  1.04 

K20 1.95  0.38 

H20 0.24  0.09 

99^91  100.21 

The  result  of  the  increase  of  magnesia  and  lime  shows 
itself  in  the  change  in  composition  of  the  dark  mineral.  The 
iron  shows  a  movement  in  the  opposite  direction;  in  the 
syenite  it  is  all  found  in  the  hornblende;  in  the  shonki- 
nite large  quantities  had  been  used  for  the  iron  ore  and 
olivine,  and  to  some  extent  for  the  biotite  before  the  augite 
began  crystallizing;  hence  it  is  not  so  prominent  as  in  the 
barkevikite. 

In  general,  however,  the  difference  is  of  like  kind  with 
that  shown  by  the  mass  analyses  of  the  rocks  and  shows 
clearly  how  the  composition  of  the  prominent  dark  mineral 
is  a  function  of  the  magma  in  which  it  is  formed.  That 
minerals  indeed  are  so  often  conditioned  by  the  magma  in 
which  they  are  formed  is  without  doubt  the  fact  that  has 
given  to  some  the  idea  that  definite  mineral  molecules  indi- 
vidualized as  such  can  exist  in  the  molten  magma. 

Recently  Johnston -Lavis  *  has  formulated  a  theory  for  the 
different  composition  of  igneous  rocks  occurring  at  the  same 
eruptive  centre  by  supposing  that  the  body  of  molten  magma 
which  gave  them  birth  was  originally  homogeneous,  but 

*  Natural  Science,  vol.  iv,  February,  1894. 


THE  HIGHWOOD  MOUNTAINS  OF  MONTANA.       433 

became  of  different  composition  on  its  outer  margin  by 
fusion  and  absorption  of  the  country  rocks  with  which  it 
came  in  contact. 

Whether  this  is  ever  so  or  not  is  fairly  a  matter  for  argu- 
ment. That  such  a  process  cannot,  however,  be  appealed  to 
as  a  general  explanation  is  clearly  shown  at  Square  Butte, 
where  the  outer  margin,  as  already  shown,  is  much  more 
basic  than  the  interior,  and  yet  the  magma  has  been  intruded 
into  sandstones  —  that  is,  rocks  much  more  acid  than  the 
original  magma. 

The  singular  white  band  which  has  been  previously  de- 
scribed as  occurring  on  the  south  side  of  Square  Butte 
presents  on  a  small  scale  the  same  process  of  differentiation 
between  the  syenite  and  shonkinite.  We  believe  that  it 
represents  what  may  be  called  a  residual  differentiation  — 
that  is,  that  after  the  main  process  had  already  taken  place 
and  the  outer  margins  of  the  laccolitic  cavity  were  filled  with 
that  magma  which  was  later  going  to  cool  and  crystallize 
into  shonkinite  this  further  differentiation  took  place  in  the 
shonkinite  fluid. 

The  latter,  probably  owing  to  increasing  viscosity,  was  not 
able  to  permit  the  white  band  fluid  to  pass  in  by  diffusion  to 
the  main  body  of  the  syenite  and  it  therefore  remained  parallel 
to  the  transition  zone  of  the  two  principal  masses. 

It  will  be  noticed  that  a  section  passing  from  the  centre 
to  the  south  of  Square  Butte  passes  twice  through  white 
feldspathic  and  twice  through  dark  augitic  rock,  if  we  take 
the  white  band  into  consideration.  Further,  that  these 
various  layers  have  a  concentric  arrangement  with  respect 
to  each  other,  and  hence  one  sees  that  Square  Butte  presents 
on  a  huge  scale  a  rude  parallel  to  those  spheroidal  masses 
which  sometimes  occur  in  granites  and  diorites,  and  which 
are  often  remarkable  for  the  regular  concentric  arrangement 
of  spherical  shells  of  varying  composition. 

Backstrom  *  has  sought  to  explain  certain  cases  of  such 
spheroidal  masses  as  portions  of  a  partial  magma  separated 

*  Geol.  Foren.  Forh.,  Stockholm,  Bd.  16,  1894,  p.  128. 
28 


434  PETROGRAPHY  OF  SQUARE  BUTTE  IN 

out  in  the  liquid  state  from  a  mother  liquor,,  in  which,  by 
sinking  temperature,  they  are  no  longer  soluble. 

Backstrb'm  has  expanded  this  idea  and  sought  a  general 
explanation  *  for  the  differentiation  of  igneous  magmas  in  a 
process  of  "liquation,"  by  which  is  meant  that  an  originally 
homogeneous  magma  by  sinking  temperature  becomes  un- 
stable and  separates  into  two  or  more  fluids  which  are 
insoluble  in  each  other  —  that  is,  non-miscible.  It  seems  to 
us  that  the  concentric  arrangement  of  parts  and  the  clear 
and  sharp  line  of  division  between  them  at  Square  Butte 
point  very  favorably  to  this  view  as  an  explanation.  Back- 
Strom,  however,  expresses  himself  as  strongly  against  the 
idea  of  "diffusion,"  by  which  we  suppose  is  meant  the  diffu- 
sion of  the  basic  oxides  toward  the  outer  cooling  surfaces. 
That  such  diffusion,  however,  can  take  place  is  clearly 
shown  at  Square  Butte,  where  it  has.  In  any  case  a  diffu- 
sion of  some  kind  must  take  place  or  the  magma  would 
remain  homogeneous.  We  do  not  see,  indeed,  that  Ba'ck- 
strom  has  advanced  any  reason  which  would  prove  that  these 
two  ideas,  diffusion  and  liquation,  necessarily  exclude  each 
other.  We  do  not  see,  in  fact,  why  both  may  not  be 
operative. 

As  a  matter  of  fact,  the  more  that  the  differentiation  of 
igneous  rocks  is  studied  the  more  evident  it  becomes  that  no 
one  simple  process  will  explain  all  cases,  but  that  to  produce 
such  results  a  variety  of  factors  must  be  included,  any  one 
or  all  of  which  may  operate  to  produce  a  given  phenomenon. 
Such,  for  example,  may  be  pressure,  change  of  temperature, 
convection  currents  (which  are  shown  by  the  "flow  structure  " 
and  parallel  arrangements  of  pheriocrysts  on  the  margins  of 
intruded  masses),  diffusion  of  certain  oxide  molecules  toward 
cooling  surfaces,  liquation  and  crystallization.  The  opera- 
tion of  these  on  molten  silicate  magmas  is  as  yet  but  little 
understood  and  much  more  must  be  done  and  learned  before 
any  generally  satisfactory  theory  for  differentiation  can  be 
advanced. 

*  Jour,  of  Geol.,  Chicago,  vol.  i,  1893,  p.  773. 


THE  HIGHWOOD  MOUNTAINS   OF  MONTANA.       435 

Whatever  may  have  been  the  causes  at  work  at  Square 
Butte,  two  things  at  least  are  evident:  that  the  basic  oxides 
concentrated  toward  the  outer  edges  and  that  the  changes 
which  produced  this  took  place  very  slowly  and  with  extreme 
regularity,  allowing  the  differentiation  to  be  very  complete 
and  thorough. 

SUMMARY. 

Square  Butte  is  a  laccolite  which  has  been  intruded  in 
Cretaceous  sandstones.  After  the  intrusion  differentiation 
took  place  in  the  liquid  mass,  the  iron,  magnesian,  and  lime 
molecules  being  greatly  concentrated  in  a  broad  exterior 
zone,  leaving  an  inner  kernel  of  material  richer  in  alumina, 
alkalies,  and  silica.  This  crystallized  into  a  sodalite-syenite, 
while  the  outer  mass  formed  a  basic  granular  rock  composed 
essentially  of  augite  and  orthoclase,  to  which  the  name  of 
shonkinite  has  been  given.  After  solidification  the  cooling 
developed  a  fine  platy  structure  throughout  the  mass  parallel 
to  the  form  of  the  laccolitic  cover.  Since  then  erosion  has 
removed  the  cover,  laying  bare  the  laccolite  and  dissecting  it, 
so  that  its  structure  is  clearly  brought  out. 

Owing  to  the  erosion  and  the  platy  parting,  the  broad 
marginal  zone  of  shonkinite  has  been  carved  into  a  wide  band 
of  singular  monoliths  which  extends  around  the  mountain  on 
its  lower  slopes. 


PETROGRAPHY  OF  THE  ROCKS  OF  YOGO  PEAK.* 

BY  L.  V.  PIRSSON. 

THE  rock  mass  of  Yogo  Peak,f  and  the  different  rock  varie- 
ties into  which  it  is  differentiated  have  already  been  described 
by  Mr.  Weed  and  the  writer.  J  In  that  article  only  brief 
petrographic  details  were  given,  sufficient  to  make  clear  the 
discussion  of  the  analyses  and  the  facts  bearing  on  theoretic 
petrography  which  comprised  its  essential  features.  It  is 
here  proposed  to  treat  these  types  in  more  detail  especially 
those  points  which  are  of  interest  to  petrographers.  The 
discussion  of  the  facts  from  a  standpoint  of  general  petrog- 
raphy is  deferred  to  the  latter  part  of  this  work. 

SYENITE  OF  YOGO  PEAK. 

That  portion  of  the  Yogo  Peak  stock  which  may  be  most 
properly  classified  as  a  syenite  comprises  the  eastern  shoulder 
of  the  elevated  mass.  The  rock  possesses  a  platy  parting  which 
causes  it  to  split  readily  and  form  piles  of  debris  above  which 
project  low  and  much-jointed  exposures  of  the  rock  in  place. 
The  joint  blocks  are  short,  stout  rhomboids,  or  heavy  plates  a 
foot  or  so  long.  They  are  very  hard  and  tough,  ring  sonor- 
ously under  the  hammer,  and  are  broken  with  difficulty,  the 
rock  being  unaltered  and  fresh. 

*  Abstract  from  Geology  and  Petrography  of  the  Little  Belt  mountains, 
Montana,  by  W.  H.  Weed  and  L.  V.  Pirsson,  20th  Ann.  Rep.  U.  S.  Geol.  Survey, 
Part  III,  pp.  471-488,  1900. 

t  Yogo  Peak  is  one  of  the  most  prominent  of  the  Little  Belt  range,  rising 
to  9000  feet  in  elevation.  It  consists  of  a  mass  or  stock  of  granular  igneous 
rock  intruded  in  Paleozoic  limestones  and  other  bedded  rocks.  At  the  contact 
the  igneous  rock  is  very  dark  and  basic  and  is  the  shonkinite  mentioned,  it 
grades  into  a  more  feldspathic  zone  of  monzonite,  which  in  turn  passes  into  the 
still  more  feldspathic  syenite,  the  first  type  described.  The  petrography  of 
these  three  types  is  discussed  in  this  abstract.  —  EDITOR. 

\  Amer.  Jour.  Sci.,  vol.  50,  1895,  p.  467. 


ROCKS  OF  YOGO  PEAK.  437 

On  a  freshly  fractured  surface  the  rock  appears  evenly 
granular,  of  moderately  fine  grain,  and  is  compact  in  character 
and  with  few  miarolitic  cavities.  The  color  is  a  medium 
gray  with  a  pinkish  tone.  Examined  with  the  lens,  it  is  seen 
to  be  chiefly  composed  of  light-colored  feldspar,  dotted  with 
small,  dark,  formless  spots  of  green  pyroxene  or  hornblende. 

The  microscope  shows  the  following  minerals  to  be  present  : 
apatite,  titanite  and  iron  ore,  pyroxene,  hornblende  and  biotite, 
orthoclase,  oligoclase,  and  quartz.  The  apatite  and  titanite 
are  of  the  usual  characters  common  to  such  rocks.  The  iron 
ore  is  not  abundant  and  occurs  in  small  grains  of  about  1  mm. 
in  diameter.  The  pyroxene  is  a  very  pale  green  diopside  and 
is  much  cracked  and  broken  up.  It  frequently  appears  like  a 
bundle  of  rods.  It  is  rarely  alone  and  generally  occurs  in 
common,  with  a  brownish-green  hornblende.  The  two  min- 
erals are  very  frequently  found  together  in  stout,  ill-shaped 
crystals  from  1  to  2  mm.  long,  the  pyroxene  forming  a  core, 
surrounded  by  the  hornblende.  In  such  cases  the  amount  of 
pyroxene  is  inversely  proportional  to  that  of  the  hornblende. 
The  appearance  and  association  of  these  two  minerals  indicate 
that  the  hornblende  is  paramorphic  after  the  pyroxene.  The 
latter  rarely  occurs  alone,  while  the  hornblende  frequently 
does  so.  Biotite  is  rare  and  occurs  only  as  occasional  brown 
pleochroic  shreds. 

Orthoclase  is  the  predominant  feldspar,  occurring  in  irregu- 
lar masses.  A  smaller  quantity  of  plagioclase  is  also  present, 
whose  optical  characters  prove  it  to  be  oligoclase.  It  is  more 
idiomorphic  than  the  orthoclase,  frequently  or  even  commonly 
occurring  in  rather  rectangular  elongated  laths,  and  is  often 
surrounded  by  a  mantle  of  orthoclase.  A  small  amount  of 
interstitial  quartz  completes  the  list  of  minerals. 

In  structure  the  rock  is  hypidiomorphic,  but  only  partly  so, 
as  the  pyroxene  and  hornblende  are  themselves  rather  ill- 
formed  and  irregular,  and  the  tendency  is  toward  an  allotrio- 
morphic  structure.  The  average  size  of  grain  is  about  1  mm. 

The  analysis  given  in  No.  I  of  the  table  shows  the  chemical 
composition  of  this  rock. 


438 


PETROGRAPHY  OF  THE 


ANALYSES  OF  SYENITES. 

i.  H.  in.             iv. 

Silica  (Si02) 61.65  59.56        61.73        1.027 

Alumina  (A1203) 15.07  17.60         17.45        0.145 

Ferric  iron  (Fe203)  ....     2.03  2.90  )        -  q ,         0.013 

Ferrous  iron  (FeO)  ....     2.25  3.38  /  0.031 

Magnesia  (MgO) 3.67  1.87          2.29        0.092 

Lime  (CaO) 4.61  3.67          4.52        0.082 

Soda  (Na20)     4.35  4.88          3.12        0.070 

Potash  (K2O) 4.50  4.40          3.88        0.048 

Water  (H20)  at  110°  .  .  .  0.26 )  1  „            .  lfi 

Water  (H20)  above  110°  .     0.41  f 

Titanic  oxide  (Ti02)  .  .  .     0.56  1.22  ?            ... 

Chromic  oxide  (O203)  .  .       tr.    x  =  0.44 

Manganese  oxide  (MnO)  .  0.09  0.03                           .  .  . 

Baryta  (BaO) 0.27  ?                ? 

Strontia  (SrO) 0.10  ?               ? 

Chlorine  (Cl) — 

Phosphoric  acid  (P205)    .  0.33  ?               ? 

Sulphuric  acid  (S03)  ...      —  ... 

Carbonic  acid  (C02)    ...      —  ... 

Lithia  (Li2O) tr. 

10016  101.32      100.09 

I.  Syenite,   Yogo   Peak.      Little   Belt    Mountains,   Montana. 
W.  F.  Hillebrand,  anal. 

II.  Syenite  Aakerite  type,  Vettakollen.     So.  Norway.     H.  0. 
Lang,  Nyt.  Mag.  for  Nat.,  vol.  30,  p.  40  (P.  Jannasch,  anal.). 

III.  "  Syenite,"    "  diorite,"    "  banatite "    Hodritsch    vale,  by 
Schemnitz,  K.  von   Hauer,  Verhand.  k.  k.  E-eichsanstalt,  1867, 
p.  82. 

IV.  Molecular  proportions  of  No.  I. 

The  analysis  is  that  of  a  syenite  with  rather  high  lime,  iron, 
and  magnesia  for  a  rock  of  this  group.  The  mineral  and 
chemical  nature  of  the  rock  show  it  to  have  a  somewhat 
dioritic  tendency,  and  in  fact  it  is  closely  related  to  the 
monzonite  group  in  which  the  feldspars  are  equal,  that  is 
approximately  the  plagioclase  equals  the  orthoclase.  It  is 
very  closely  related  to  certain  of  the  syenites  which  have 
been  called  Akerites,  as  the  analysis  of  one  of  them  tends 


ROCKS   OF  YOGO  PEAK.  489 

to  show.  Moreover  the  description  of  these  akerites  as  given 
by  Brogger,*  with  their  rectangular  zonal  feldspars,  applies 
closely  to  this  rock.  On  the  other  hand,  its  relation  to  cer- 
tain rocks  which  have  been  variously  placed,  sometimes 
among  the  syenites,  sometimes  among  the  diorites,  is  shown 
by  the  close  agreement  with  the  analysis  of  the  rock  from 
the  Hodritsch  vale  near  Schemnitz.  All  these  types  clearly 
belong  in  a  group  by  themselves  and,  following  the  proposal 
of  Brogger,!  they  may  well  be  considered,  an  intermediate 
group  between  the  normal  syenites  and  diorites  and  called 
banatites,  after  the  old  name  used  by  Von  Cotta.  Thus  the 
rock  of  Yogo  Peak,  although  here  called  a  syenite  as,  under 
a  broad  grouping,  according  to  present  ideas  of  rock  classi- 
fication, it  would  undoubtedly  be  so  called,  would  for  petro- 
graphical  purposes  be  better  designated  as  a  banatite.  Its 
connection  with  the  monzonite  of  Yogo  Peak  as  part  of 
a  single  geologic  mass  is  extremely  interesting,  as  it  shows 
that  grouping  and  connection  exhibited  by  nature  itself  which 
Brogger  has  suggested  on  theoretic  grounds. 

By  assuming  all  the  alumina  in  feldspar  and  taking  the 
equivalent  of  soda,  potash,  and  lime  for  it  and  then  assigning 
sufficient  ferrous  iron  to  convert  the  ferric  iron  into  magnetite 
we  may  calculate  with  pretty  close  approximation  to  truth 
the  mineral  composition.  For  the  remaining  lime,  iron,  and 
magnesia  are  to  be  divided  between  pyroxene  and  horn- 
blende, which  is  readily  done  while  the  excess  of  silica  rep- 
resents the  quartz.  This  gives 

Magnetite  3.1 

Pyroxene  5.4 

Hornblende  12.9  components. 

Anorthite  7.5  Dark  21.4 

Albite  37.5  Light  78.6 

Orthoclase  27.5  100.0 

Quartz  6.1 

100.0 

*  Syenit  pegmatit  gange  Sud  Norwegens,  Groth's  Zeit.  f.  Kryst,  vol.  16, 
p.  51. 

t  Triadischen  Eruptionsfolge  bei  Predazzo. 


440  PETROGRAPHY  OF  THE 

The  average  plagioclase  would  be  Ab^An^  but  as  consider- 
able of  the  albite  molecule  is  doubtless  with  the  orthoclase, 
the  oligoclase  present  does  not  average  so  much  soda  as  this. 

Local  varieties  of  the  syenite.  —  Towards  the  high  east 
shoulder  of  Yogo  Peak  which  descends  to  a  saddle  on  the 
ridge,  the  talus  forming  this  slope  shows  a  variety  of  the  rock 
in  which  the  plagioclase  diminishes  almost  to  the  vanishing 
point  and  the  rock  therefore  assumes  the  character  of  a 
normal  and  typical  syenite;  in  other  respects  its  character 
is  that  of  the  type  just  described  and  it  cannot  indeed  in 
the  hand  specimen  be  distinguished  from  it.  The  variation 
is  probably  local  but  it  has  a  certain  petrologic  significance 
which  will  be  treated  of  in  another  place. 

At  the  prospect  mining  shaft  which  has  been  sunk  not 
far  from  the  contact  on  the  south  side  of  Yogo  Peak  in  the 
igneous  rock  there  occurs  a  light-colored  rock  which  is  an- 
other variation  of  the  banatite  in  that  it  represents  a  more 
dioritic  phase ;  the  lath-like  plagioclases  clearly  predominate 
over  the  alkali  feldspar  and  form  the  main  rock  constituent. 
It  is  interesting  to  note  in  this  variety  that  the  hornblendes 
although  quite  compact  and  appearing  on  the  whole  as  if 
original  yet  occasionally  carry  interior  cores  or  fragments 
of  pale  green  diopside.  What  the  exact  relation  of  this 
diorite-like  facies  is  to  the  shonkinite  and  monzonite  which 
are  the  main  rock  types  of  the  vicinity  could  not  be  learned, 
as  it  is  not  apparent  at  the  surface,  but  it  must  certainly 
be  quite  limited  in  amount  when  compared  with  them. 

MONZONITE. 

This  name  has  been  applied  to  a  massive  igneous  rock 
occurring  at  Monzoni  in  the  Tyrol  which  has  usually  been 
classified  under  the  syenites,  of  which  it  has  been  consid- 
ered a  variety  rich  in  plagioclase  and  in  the  darker  ferro- 
magnesian  minerals,  especially  pyroxene.  It  has  been  shown 
in  recent  years  that  this  type  of  rock  is  not  confined  to  the 
vicinity  of  Monzoni,  but  occurs  elsewhere  in  sufficient  abun- 
dance to  warrant  the  proposition  that  the  name  shall  no  longer 


ROCKS   OF  YOGO  PEAK.  441 

be  considered  that  of  a  mere  variety  of  syenite  but  of  an 
independent  rock  group,  of  the  same  order  of  significance 
as  that  of  syenite  and  diorite,  to  be  applied  to  those  rocks 
in  which  the  alkali  and  lime  soda  feldspars  are  about  equally 
balanced,  thus  avoiding  the  difficulties  of  classifying  such 
rocks  either  with  the  syenites  or  the  dio rites.  *  In  the  former 
article  on  Yogo  Peak  by  Mr.  Weed  and  the  writer  f  the  latter 
in  the  petrographic  description  showed  that  the  type  of  rock 
forming  the  middle  knob  of  the  peak  was  of  unusual  charac- 
ter, in  which  alkali  feldspars  were  of  about  equal  amount 
with  plagioclase,  and  the  name  "  yogoite  "  was  proposed  for 
this  type. 

Later,  J  however,  recognizing  that  "yogoite  "  is  essentially 
the  same  rock  as  that  from  Monzoni  and  Predazzo  both  chemi- 
cally and  in  its  mineral  composition,  the  name  "yogoite" 
was  withdrawn  for  the  older  and  better  known  term.  Rocks 
of  this  character  have  been  found  in  several  localities  in 
Montana  and  the  number  of  occurrences  in  this  portion  of 
the  Rocky  Mountain  area  will  no  doubt  be  increased  in  the 
future.  It  can  scarcely  be  doubted  also  that  many  types  of 
rocks  hitherto  placed  under  diorites  or  syenites  by  different 
petrographers  really  belong  in  this  general  group  and  that 
the  future  will  show  the  type  to  be  a  not  uncommon  one. 
In  the  localities  so  far  described  at  Monzoni  and  Predazzo 
in  Tyrol,  at  the  Bearpaw  Mountains,  and  here  at  Yogo  Peak 
and  also  in  the  Highwood  Mountains  in  Montana,  the  rock 
does  not  appear  geologically  alone  and  independent  but  is 
accompanied  by  more  feldspathic  types  on  the  one  hand  and 
more  dark-colored,  basic,  augitic  varieties  on  the  other.  It 
is  thus  part  of  a  differentiated  complex  and,  considering  the 
very  medium  chemical  character  it  possesses,  as  a  sort  of 
petrographic  mean,  this  should  be  expected. 

At  Yogo  Peak  the  rock  occurs  most  typically  and  best  ex- 

*  Bro'gger,  Eruptivgesteine  des  Kristianiagebietes,  ii,  Predazzo. 
f  Amer.  Jour.  Sci.,  vol.  50,  p.  467,  1895. 

J  Weed  &  Pirsson,  Bearpaw  Mountains  of  Montana,  Amer.  Jour.  Sci.,  vol. 
i,  p.  357,  1896. 


442  PETROGRAPHY  OF  THE 

posed  at  the  central  one  of  the  three  prominent  knobs  form- 
ing the  peak.  It  grades  into  the  banatite  variety  of  syenite, 
previously  described  which  forms  the  eastern  shoulder  on  the 
one  hand  and  into  the  shonkinite  of  the  western  outcrops  and 
exposures  on  the  other. 

The  rock  occurs  in  short  blocks  and  is  very  firm  and  tough. 
On  a  fresh  fractured  surface  it  is  of  a  rather  dark  gray  with 
a  greenish  tone  and  appears  of  a  medium  granularity.  It  is 
clearly  seen  to  be  somewhat  mottled  by  the  contrast  between 
the  light  colored  feldspathic  portion  and  the  darker  colored 
ferro-magnesian  minerals  and  recalls  in  its  appearance  many 
diorites ;  the  dark  minerals  appear  to  make  up  half  the  bulk 
of  the  rock.  The  reflection  of  light  from  numerous  biotite 
cleavages  of  small  size  is  also  noticeable. 

Under  the  microscope  the  minerals  seen  are  iron  ore,  apa- 
tite, biotite,  pyroxene,  hornblende,  plagioclase,  alkali  feld- 
spars, and  quartz. 

The  iron  ore  is  not  present  in  large  amount,  but  is  seen  in 
scattered  grains  usually  attached  to  pyroxene  and  biotite. 
The  apatite  is  not  abundant  and  shows  nothing  of  especial 
interest. 

The  pyroxene  is  a  clear  pale  green  diopside  of  wide  extinc- 
tion angle  and  rather  idiom orphic  in  form.  It  is  pretty  free 
from  inclusions  save  those  of  iron  ore  and  apatite ;  in  a  few 
cases  some  of  a  brownish  substance  which  may  be  glass  were 
seen.  It  is  very  fresh  and  unaltered  except  for  its  connection 
with  hornblende.  It  is  the  most  abundant  ferro-magnesian 
mineral. 

The  hornblende  is  of  the  olive-green  color  usually  seen  in 
common  hornblende,  strongly  pleochroic,  and  is  generally 
seen  surrounding  or  attached  to  the  diopside.  It  occurs  in 
places  penetrating  the  latter  in  small  flakes  or  rods,  and  some- 
times the  diopside  is  quite  spotted  with  these  bits  of  horn- 
blende. When  in  larger  pieces  it  does  not  have  any  distinct 
idiomorphic  form  and  all  these  facts  go  to  show  very  clearly 
its  secondary  paramorphic  character.  Nowhere  does  it  show 
those  evidences  of  primary  character  which  Iddings  has  so 


ROCKS  OF  YOGO  PEAK.  443 

well  described  and  figured  in  the  intergrowths  of  hornblende 
and  pyroxene  in  the  diorite  of  Electric  Peak.*  An  estimate 
made  on  the  sections  places  it  as  being  one-tenth  of  the  diop- 
side  in  amount. 

The  biotite  is  pleochroic  in  tones  of  pale  yellow  and  olive 
brown,  basal  sections  are  a  deep  umber  brown.  It  is  quite 
idiomorphic  and  has  the  usual  apatite  and  iron  ore  inclusions. 

The  plagioclase  is  rather  variable ;  studies  of  it  according 
to  recent  methods  show  that  it  is  mostly  andesine,  in  small 
part  oligoclase,  and  even  a  little  albite  is  present.  It  occurs 
in  rather  broad  tabular  forms  giving  in  general  idiomorphic 
sections :  sometimes  it  is  seen  in  rather  slender  laths  which 
are  always  smaller  than  the  table  mentioned  above  and  while 
they  are  generally  Carlsbad  twins  they  often  show  no  albite 
twinning  or  at  best  but  one  or  two  strips ;  they  are  invari- 
ably of  andesine.  The  larger  tables  on  the  contrary  always 
show  albite  twinning,  usually  in  very  fine  lamellae,  and  some- 
times are  not  Carlsbad  twins ;  they  are  more  irregular  in  their 
composition ;  are  sometimes  zonally  built  with  basic  cores 
and  sometimes  consist  of  varying  irregular  masses  without 
any  regular  crystallographic  or  zonal  arrangement,  but  with 
the  albite  twinning  passing  through  as  if  the  crystal  were 
entirely  homogeneous.  Thus  in  these  crystals  while  andesine 
is  the  most  common  proportion,  they  vary  through  oligoclase 
to  albite. 

The  alkali  feldspar  is  mostly  a  soda  orthoclase  but  this 
contains  a  microperthite-like  intergrowth  of  another  feldspar 
that  is  believed  to  be  albite,  but  it  is  present  in  such  narrow 
lamellae  that  this  could  not  be  proved ;  moreover  it  does  not 
show  the  albite  twinning.  All  that  can  be  safely  said  of  it  is 
that  it  is  another  feldspar  and  not  quartz.  The  intergrowths 
are  not  exactly  like  the  usual  microperthitic  lamellae  of  albite 
but  more  nearly  resemble  micrographic  intergrowths  of  quartz 
and  orthoclase ;  it  does  not  require  a  very  high  power  to  see 
them  clearly. 

The  calculation  of  the  chemical  analysis  shows  that  the 

*  12th  Ann.  Rep.  U.  S.  Geol.  Surv.     Washington,  1892,  p.  606. 


444 


PETROGRAPHY  OF  THE 


total  average  alkali  feldspar  has  the  composition  Oi'iAbi  but 
the  microscope  shows  that  although  this  may  be  the  sum 
total  there  is  considerable  variability  in  the  manner  in  which 
the  albite  and  orthoclase  molecules  are  arranged. 


ANALYSES  OP  MONZONITES. 


I. 

II. 

m. 

IV. 

V. 

VI. 

VIa. 

VII. 

Si02 

54.42 

52.81 

52.05 

51.00 

54.20 

52.89 

53.0 

0.907 

A1203 

14.28 

15.66 

15.02 

17.21 

15.73 

15.58 

16.0 

0.139 

Fe203 

3.32 

3.06 

2.65 

2.41 

3.67 

3.03 

30 

0.021 

FeO 

4.13 

4.76 

5.52 

4.23 

5.40 

481 

5.0 

0.057 

MgO 

6.12 

4.99 

5.39 

6.19 

3.40 

6.22 

5.0 

0.152 

CaO 

7.72 

7.57 

8.14 

9.15 

8.50 

8.21 

8.0 

0.139 

Na20 

3.44 

3.60 

3.17 

2.88 

3.07 

3.23 

3.0 

0.055 

K20 

4.22 

4.84 

6.10 

4.93 

4.42 

4.90 

5.0 

0.045 

H20  -  110° 
H2O  +  110° 

0.38 
0.22 

0.93) 
0.16  } 

0.35 

0.63 

0.50 

0.51 

0.5 

Ti02 

0.80 

0.71 

0.47 

0.13 

0.40 

0.56 

0.5 

.  .  . 

Fl 

tr. 

Cl 

.'  ' 

0.07 

0.24 

tr. 

0.11 

P205 

0.59 

0.75 

0.21 

0.33 

0.50 

0.47 

0.5 

.  .  . 

SOo 

tr. 

0.02 

0.03 

kj  vy<j 

Cr^Oo 

tr. 

v->i  2^3 

MnO 

0.10 

tr. 

tr. 

tr. 

0.70 

.  .  • 

.  .  . 

.  .  • 

BaO 

0.32 

0.24 

0.42 

0.34 

? 

0.33 

0.3 

.  .  . 

SrO 

0.13 

0.09 

0.28 

0.14 

-2 

0.15 

0.2 

.  .  . 

Li20 

tr. 

tr. 

100.19      100.24      100.03       99.60      100.49      100.00    100.00 

I.  Monzonite  of  Yogo  Peak.     W.  F.  Hillebrand,  anal. 

II.  Monzonite  of  Beaver  Creek,  Bearpaw  mountains  (Weed  and 
Pirsson,  Am.  Jour.  Sci.,  vol.  50,  1895,  p.  357).    H.  N.  Stokes,  anal. 

III.  Monzonite  of  Highwood  Peak,  High  wood  mountains  (Bull. 
U.  S.  Geol.  Surv.,  No.  148,  p.  154).     E.  B.  Hurlburt,  anal. 

IV.  Monzonite  of  Middle  Peak,  Highwood  mountains  (Loc.  cit. 
supra).     E.  B.  Hurlburt,  anal. 

V.  Monzonite  of  Monzoni  (Brogger,  Erupt.  Gest.,  Predazzo, 
1895,  p.  24).     V.  Schmelck,  anal. 

VI.  Average  of  above  analyses  reduced  to  100. 

VII.  Molecular  proportions  of  No.  I. 

The  structure  of  the  rock  is  a  purely  hypidiomorphic  gran- 
ular one.  There  is  a  strong  tendency  for  the  ferro-magnesian 
elements  to  be  together  and  also  for  little  areas  to  occur  in 


ROCKS   OF   YOGO  PEAK.  445 

which  plagioclase  is  very  abundant,  others  in  which  it  is  nearly 
absent  and  unstriated  alkali  feldspar  rules.  Thus,  while 
taken  in  mass  the  composition  of  the  rock  is  very  homogene- 
ous, on  a  microscopic  scale  it  is  variable  and  it  is  hard  to  bring 
into  the  field  of  the  microscope,  except  with  extremely  low 
powers,  an  area  that  would  be  typical  of  the  rock  as  a  whole. 
The  alkali  feldspar  shows  always  a  tendency  to  a  broad  poi- 
kilitic  character  tending  to  surround  the  other  minerals.  An 
extremely  minute  amount  of  interstitial  quartz  needs  no  fur- 
ther mention  ;  its  role  as  rock  component  is  here  without  sig- 
nificance. 

An  analysis  of  the  rock  by  Dr.  Hillebrand  is  shown  in  the 
above  table,  and  with  it  published  analyses  of  four  other 
monzonites  from  different  localities;  the  older  analyses  are 
full  of  analytical  errors  and  are  not  to  be  trusted ;  it  will  be 
noticed  how  nearly  all  these  agree  and  how  little  any  one  of 
them  departs  from  the  mean  of  the  whole  five  given  in  No.  VI. 
This  mean  may  be  taken  then  as  the  typical  composition  of  a 
monzonite,  or  as  expressed  in  the  nearest  whole  numbers  and 
given  in  No.  VIa.  The  feature  of  this  chemical  composition 
is  the  very  medium  character  expressed  throughout;  in  all 
respects  the  monzonites  stand  as  a  mean  between  the  different 
rock  groups. 

If  we  make  two  or  three  assumptions,  as  follows,  that  the 
biotite  is  nearly  or  practically  free  from  ferric  iron  and  agrees 
with  the  biotite  of  Monzoni  which  has  been  analyzed,  in  this 
regard :  that  the  replacement  of  magnesia  by  ferrous  iron  is 
similar  in  the  minerals  into  which  these  enter  and  that  the 
amount  of  hornblende  is  one-tenth  that  of  diopside  as  shown 
by  estimates  made  from  the  sections,  we  may  calculate  from 
the  analysis  and  the  table  of  molecular  proportions  given 
in  No.  VII  the  mineral  composition  of  the  rock.  None  of 
these  assumptions  is  absolutely  correct,  but  all  of  them  must 
be  approximately  so,  hence  the  following  table,  while  not 
absolutely  accurate,  must  represent  the  composition  pretty 
closely. 


446  PETROGRAPHY  OF  THE 

Magnetite 5.1        Andesine  (An2Ab3) 27.2 

Biotite 12.1         Soda-orthoclase  (Oi'iAbi)  ....  30.4 

Diopside 20.7        Total  feldspars 57.6 

Hornblende    ....    4.5        Total  ferro-magnesian  minerals  42.4 

Anorthite 11.3  77:7:7: 

Albite 30.1 

Orthoclase 16.2 

100.0 

The  amount  of  the  albite  molecule  present  is  just  sufficient 
to  turn  the  anorthite  into  the  andesine  demanded  by  the 
microscopic  study  and  have  enough  left  to  convert  the  ortho- 
clase  into  a  soda  orthoclase  where  the  relations  are  as  1:1  and 
this  is  a  very  common  ratio  for  soda  orthoclase,  as  indeed  on 
chemical  grounds  we  should  be  obliged  to  expect.  The  calcu- 
lation shows  also  that  the  plagioclase  and  alkali  feldspar 
present  are  equal  and  again  shows  the  impossibility  of  classify- 
ing these  rocks  logically  either  as  syenites  or  diorites.  The 
large  proportion  of  ferromagnesian  minerals  present,  forming 
two-fifths  of  the  whole,  also  shows  the  middle  position  occu- 
pied by  this  type. 

SHONKINITE. 

This  name  has  been  given  to  dark-colored  basic  granitoid 
rocks  consisting  chiefly  of  orthoclase  (or  alkali  feldspar)  and 
augite,  but  in  which  unlike  the  syenites,  which  are  feldspathic 
rocks,  the  augite  predominates  producing  an  augitic  or  as  one 
might  say  a  gabbroid  rock.  Besides  these  chief  components, 
olivine,  biotite,  and  iron  ore  among  the  dark-colored  minerals 
and  plagioclase  among  the  light-colored  ones  may  be  present 
as  accessory  components  in  considerable  amount,  —  but  the 
orthoclase  and  augite  are  in  all  cases  the  determinant  minerals. 
This  type  of  rock  is  closely  related  to  theralite  in  that  both 
are  dark-colored  basic  augitic  types  and  both  are  apt  to  occur 
associated  with  other  types  of  rocks  rich  in  alkalies,  but  thera- 
lite, the  granular  plutonic  equivalent  of  the  tephrites,  has  pla- 
gioclase and  nephelite  as  its  determinant  white  minerals. 

The  first  shonkinite  described  was  that  from  Square  Butte 


ROCKS  OF  YOGO  PEAK.  447 

in  the  Highwood  mountains  by  Mr.  Weed  and  the  author* 
and  later  the  occurrence  at  Yogo  Peak  was  briefly  given.f 
This  account  it  is  now  proposed  to  supplement  by  further 
details  and  to  mention  another  occurrence  in  this  district. 
Besides  these  occurrences  in  the  Little  Belt  and  Highwood 
mountains,  shonkinite  has  been  described  from  localities  in 
the  Bearpaw  mountains,!  and  it  appears,  as  will  be  shown 
later,  to  occur  at  Monzoni  in  the  Tyrol,  and  doubtless  other 
localities  will  be  found  as  knowledge  of  the  type  becomes 
better  known  and  petrographic  research  progresses. 

SHONKINITE  OF  YOGO  PEAK. 

At  Yogo  Peak  the  shonkinite  forms  the  rock  masses  of  the 
western  end,  abutting  against  the  sediments  and  it  also  occurs 
about  four  miles  northeast  on  the  ridge  running  out  in  that 
direction  from  Yogo  Peak.  Here  again  it  is  found  in  contact 
with  the  limestones,  while  to  the  south  it  is  bordered  by  the 
acid  feldspathic  rocks.  This  is  at  the  head  of  one  of  the  head 
branches  of  Running  Wolf  Creek.  Whether  the  shonkinite 
forms  everywhere  an  exterior  zone  of  this  great  intrusion  in 
the  sedimentary  beds  as  it  does  at  Square  Butte  in  the  High- 
wood  mountains  and  in  other  localities  seems  rather  doubtful 
and  cannot  be  positively  told  from  the  lack  of  exposures,  but 
it  certainly  does  in  part,  and  wherever  it  appears  in  connec- 
tion with  this  intrusion  it  is  in  its  proper  position  as  the 
exterior  portion  of  a  differentiated  mass. 

The  shonkinite  rock  does  not  possess  the  thick,  platy  part- 
ing that  prevails  in  the  monzonite  and  syenite  to  the  east, 
but  has  an  exceedingly  massive  character,  giving  rise  to  bold, 
heavy  crags,  often  of  curious  shapes,  which  rise  abruptly 
from  small  grassy  plots  lying  between  them.  The  rock  is 
exceedingly  tough  and  breaks  under  the  hammer  with  great 
difficulty.  On  a  fresh  fracture  it  is  of  a  very  dark  stone  color, 

*  Bull.  Geol.  Soc.  America,  vol.  6,  p.  389,  1894. 
t  Am.  Jour.  Sci.,  vol.  50,  1895,  p.  467. 

\  Weed  &  Pirsson,  Bearpaw  Mountains  of  Montana,  Amer.  Jour.  Sci.,  vol.  i, 
1896,  p.  351. 


448  PETROGRAPHY  OF  THE 

and  at  first  glance  recalls  many  coarse,  dark  gabbros.  On 
inspection  it  appears  that  the  quantity  of  ferro-magnesian 
minerals  is  very  large,  and  the  eye  is  caught  by  the  reflection 
of  numerous  plates  of  a  dark  brownish  biotite,  which  average 
several  millimeters  in  diameter.  With  the  lens  a  great 
abundance  of  small  augites  are  also  seen  in  the  feldspathic 
constituent. 

At  places  and  especially  towards  the  contact  there  is  con- 
siderable variation  in  the  grain  of  this  type ;  it  sometimes 
occurs  very  much  finer  than  the  normal  type  mentioned  above, 
and  on  the  other  hand  at  the  extreme  west  end  of  the  peak  a 
variation  is  found  that  forms  large,  irregular  masses,  the  rock 
being  noticeable  for  the  very  large,  spongy,  biotite  crystals 
which  it  carries.  These  biotites  are  at  times  1  cm.  across  a 
cleavage  face.  They  are  made  up  of  a  number  of  smaller, 
nearly  similarly  oriented  individuals  mixed  in  with  other  con- 
stituents. Although  the  mica  is  really  subordinate  in  amount 
to  the  other  minerals,  it  has  the  appearance  of  being  predomi- 
nant, and  the  rock  seems  at  first  glance  to  be  almost  wholly 
made  up  of  these  coarse  biotite  crystals  and  has  a  very  coarse- 
grained, curious  appearance.  Examination  with  the  lens  shows 
that  although  the  biotite  thus  appears  so  important  it  is  merely 
because  the  crystals  reflect  the  light  from  their  cleavage  sur- 
faces and  thus  stand  out  more  prominently  than  the  others; 
moreover  they  are  very  poikilitic  and  filled  with  augite  grains. 
Thus  the  actual  amount  of  biotite  is  less  than  that  of  either 
augite  or  orthoclase. 

Under  the  microscope  the  minerals  noted  are  iron  ore, 
apatite,  augite,  hornblende,  biotite,  olivine,  plagioclase,  and 
soda-orthoclase. 

Iron  ore  as  an  actual  component  of  the  rock  is  almost 
entirely  wanting ;  in  one  phase  a  few  scattered  grains  sur- 
rounded by  coats  of  biotite  were  observed,  but  in  the  other 
sections  representing  different  phases  and  areas  of  the  shon- 
kinite  mass  it  may  be  said  to  be  entirely  wanting.  This  is  a 
very  striking  feature  for  so  dark  and  basic  a  type,  which,  as 
the  analyses  show,  possesses  considerable  of  the  oxides  of  iron ; 


ROCKS  OF  YOGO  PEAK.  449 

it  is  therefore  clear  that  it  has  gone  into  the  f erro-magnesian 
minerals  present,  and  the  green  color  and  character  of  much 
of  the  biotite  indicates  that  it  must  approach  lepidomelane  in 
composition.  It  should  be  stated,  also,  that  a  very  small 
amount  of  iron  ore  from  the  olivine  resorptions,  to  be  presently 
described,  is  also  present,  but  this  is,  in  a  way,  secondary  and 
confined  to  these  occasional  minute  areas. 

The  apatite  present  in  short,  stout  crystals  shows  nothing 
of  especial  interest.  The  amount  of  phosphoric  anhydride  in 
the  analysis  proves  that  two  and  three  tenths  per  cent  is 
present,  while  the  fluorine  shows  it  to  be  a  fluor-apatite. 
The  augite  is  a  pale  greenish  diopside-like  pyroxene  of  a 
very  wide  extinction  angle.  The  prismatic  cleavage  is  well 
developed,  but  it  shows  no  other,  and  no  trace  of  any  diallage- 
like  character.  It  is  quite  idiomorphic,  especially  in  the 
prismatic  zone,  being  bounded  by  the  faces  #(100),  w(110), 
and  6(010)  which  have  generally  about  an  equal  development. 
The  ends  are  less  well  developed,  and  are  apt  to  be  rounded 
off,  the  habit  is  short,  thick,  columnar.  It  contains  inclusions 
of  biotite,  less  rarely  of  glass  or  iron  ore ;  these  inclusions 
are  infrequent.  In  size  the  crystals  vary  from  one-tenth  to 
one  mm. 

Hornblende  is  not  common,  and  its  character  and  associa- 
tions are  such  as  to  lead  to  the  belief  that  it  is  secondary  as 
described  under  the  monzonite  of  Yogo  Peak,  its  color,  lack 
of  definite  form,  association  with  pyroxene  are  similar,  but  it 
is  rather  less  in  amount. 

Olivine  and  its  resorption  bands.  —  The  olivine,  in  the 
most  basic  type,  that  is,  the  one  containing  the  coarse  poik- 
ilitic  biotite,  is  mostly  very  fresh  and  clear,  but  in  a  few 
places  altered  to  a  yellowish-red  micaceous  substance,  one  of 
the  well-known  alterations  of  olivine  which  need  not  be 
further  mentioned.  The  olivine  has  no  good  crystal  outline, 
but  is  in  irregular  masses.  It  has  as  inclusions  shreds  of 
mica,  sometimes  an  ore  grain,  and  occasional  little  darker 
shadow-like  spots  which,  when  examined  with  very  high 
powers,  are  seen  to  be  skeleton  magnetites  which  present 

29 


450  PETROGRAPHY  OF   THE 

wonderful  patterns  of  intricate  grating  structures.  They  re- 
semble somewhat  similar  growths  which  have  been  previously 
described  by  other  petrographers. 

The  most  interesting  thing  in  regard  to  the  olivines  is  the 
resorption  phenomena  they  show.  In  the  more  basic  and  coarse- 
grained phase  they  are  quite  unaltered  except  that  they  seem 
somewhat  rounded  and  where  they  come  against  alkali  feldspar 
there  is  generally  a  band  of  green  mica  separating  the  two. 
From  this  character  they  pass,  in  other  phases  of  the  shonkinite, 
into  types  which  are  surrounded  by  zones  as  is  often  the  case 
in  gabbros.  The  zones,  however,  are  of  somewhat  different 
character  from  those  seen  in  the  gabbros.  Here  the  olivine  is 
surrounded  by,  first,  a  band  of  granules  of  a  mineral  of  high 
refraction  and  rather  low  birefringence,  whose  general  charac- 
ters indicate  it  to  be  enstatite ;  the  granules  are  too  small  in 
size  and  confused  for  positive  identification,  but  this  also 
seems  most  probable  considering  the  composition  of  olivine. 
Next  to  this  comes  a  band  of  green  biotite,  and  then  the 
feldspar.  The  iron  in  the  olivine  separates  out  as  iron  ore  in 
black  grains.  This  process  goes  on  until  no  olivine  is  left  at 
all ;  only  a  yellowish  mica-like  substance  dotted  full  of  ore 
grains  shows  where  the  core  of  the  original  crystal  was.  From 
this  stage  they  may  be  traced  gradually  by  unaltered  pieces 
of  olivine  into  the  unchanged  crystals. 

But  the  most  interesting  point  in  regard  to  this  change  is 
that  it  is  directly  proportional  to  the  amount  of  feldspar 
which  the  rock  contains.  In  the  most  basic,  least  feldspathic 
type  of  shonkinite  the  olivines  as  noted  above  are  unaltered, 
or  surrounded  only  by  a  band  of  biotite  where  they  touch  the 
feldspar;  in  the  more  feldspathic  types  they  begin  to  be 
surrounded  by  the  resorption  bands,  but  there  is  generally 
some  olivine  substance  left,  though  not  always.  In  the  mon- 
zonite,  a  much  more  feldspathic  phase  of  the  Yogo  Peak 
mass,  these  resorptions  of  olivine  occur  but  they  are  always 
resorptions ;  no  olivine  substance  is  seen  and  they  are,  more- 
over, not  nearly  so  common.  In  the  syenite  (banatite)  certain 
groupings  of  iron  ore  and  biotite  suggest  the  same  thing,  but 


ROCKS   OF  YOGO  PEAK.  451 

are  not  conclusive.  It  is  indeed  interesting  as  a  speculation 
as  to  whether  these  olivines  were  formed  before  differentiation 
took  place  in  the  mass  or  after  it. 

The  resorption  zones,  or  "  reaction  rims  "  as  they  have  been 
called,  which  occur  around  olivines  in  the  p^agioclase  rocks 
have  been  so  well  described  and  their  origin  discussed  *  that 
they  need  no  further  mention  here,  but  it  may  be  said  that  the 
idea  that  they  could  have  been  formed  in  the  shonkinite  under 
discussion  by  any  dynamic  metamorphic  processes  is  not  ten- 
able for  a  moment ;  it  does  not  even  need  to  be  discussed  — 
we  are  dealing  with  fresh  rocks  of  a  recent  geologic  period, 
breaking  up  through  unaltered  sedimentary  beds. 

When  we  consider  the  chemical  composition  of  the  minerals 
involved,  the  cause  and  character  of  these  resorption,  or 
"reaction,"  phenomena  in  the  shonkinite  become  quite  clear. 
If  we  consider  that  out  of  the  original  magma  olivine  was 
one  of  the  first  minerals  to  separate,  it  was  because  a  mineral 
of  that  composition  was  capable  of  forming,  was  insoluble  in 
the  resulting  and  residual  magma,  or  capable  of  existing  in  it. 
As  the  process  of  crystallization  proceeded,  however,  and  the 
pyroxene,  biotite,  etc.,  crystallized  out,  the  residual  magma 
became  richer  in  alkalies  and  alumina  until  it  eventually 
solidified  as  alkali  feldspar.  When  this  stage  was  reached 
the  olivine  was  no  longer  insoluble  in  the  molten  feldspathic 
magma  and  redissolving  and  the  magma  crystallizing,  the 
following  reaction  took  place : 

Olivine.  Orthoclase.  Hypersthene.  Biotite. 

5(MgFe)2Si04  +  K2Al2Si6O16  =  8(MgFe)SiO3  +  K2(MgFe)2Al2(SiO4)8 

That  is,  the  olivine  and  orthoclase  give  rise  to  hypersthene  and 
biotite,  and  very  naturally  the  hypersthene,  the  mineral  richest 
in  magnesia,  lies  next  to  the  olivine,  while  the  biotite,  rich  in 
alkali  and  alumina,  lies  next  to  the  feldspar. 

Thus  it  is  very  easy  to  see  why  on  purely  chemical  grounds 
the  formation  of  such  zones  and  their  composition  may  be 
both  expected  and  explained. 

*  Rosenbusch,  Mass.  Gest.,  1895-6,  p.  314. 


452  PETROGRAPHY  OF  THE 

It  is  to  be  noted  that  lime,  which  plays  such  an  important 
part  in  the  zones  around  the  oli vines  in  the  gabbros,  is 
entirely  absent  in  the  above.  In  one  or  two  cases  slender 
needles  were  seen  in  the  outer  zone,  and  it  may  be  that  lime 
has  been  present  and  a  little  hornblende  formed  as  in  the 
gabbros.  This  is  exceptional  in  the  shonkinite  and  not  the 
rule. 

Feldspars.  —  The  feldspars  in  the  shonkinite  are  somewhat 
variable,  especially  the  plagioclase.  This  is  sometimes  pres- 
ent and  sometimes  wholly  absent,  and  this  within  small  areas, 
even  within  that  of  an  ordinary  thin  section. 

It  is  usually  in  the  form  of  laths  sometimes  very  small  and 
narrow,  others  broader  and  more  columnar.  It  varies  from 
interior  cores  as  basic  as  a  labradorite  Ab3An4  to  outer  rims 
of  andesine  Ab5An3;  both  albite  and  Carlsbad  twins  are 
generally  present.  The  noticeable  feature  of  this  plagioclase 
is  its  strong  idiomorphic  character,  and  this  is  especially 
noticeable  when  it  lies  imbedded  in  the  soda  orthoclase.  In 
some  places  within  a  very  minute  area  a  very  considerable 
quantity  of  these  plagioclase  prisms  will  be  heaped  together 
surrounded  by  broad  regions  quite  destitute  of  them.  Its 
total  amount  is  small,  and  considered  altogether  it  plays  only 
the  role  of  an  accessory  constituent.  It  seems  to  depend  on 
the  relation  between  pyroxene  and  biotite  to  some  extent; 
thus  in  the  more  basic  phases  where  augite  is  very  abundant 
and  its  prisms  thickly  crowded,  the  plagioclase  is  almost 
wholly  wanting  because  the  lime  has  all  united  with  the 
magnesia  and  iron  in  its  production,  while  in  those  areas 
where  it  is  not  so  common  the  magnesia  and  iron  combined 
with  alumina  and  potash  to  form  biotite  and  this  permitted 
the  lime  to  enter  into  plagioclase  with  the  soda. 

The  alkali  feldspar  ranks  with  the  augite  as  the  most 
important  rock  constituent.  In  sections  perpendicular  to 
the  obtuse  positive  bisectrix,  that  is  approximately  parallel 
to  6(010),  the  basal  cleavage  is  easily  seen  and  is  usually 
good;  at  times  a  cleavage  crosses  this  at  64°,  which  is  prob- 
ably parallel  to  the  prism,  a  not  unusual  phenomenon  in 


ROCKS   OF  YOGO  PEAK.  453 

alkali  feldspars:  this  gives  the  direction  of  the  vertical 
axis  and  enables  the  section  to  be  oriented,  and  it  is  then 
found  that  the  extinction  lies  10°  in  the  obtuse  angle, 
that  is,  is  positive,  and  therefore  the  feldspar  is  a  soda 
orthoclase.  This  is  shown  also  by  its  watery,  moire*  appear- 
ance and  other  phenomena  which  show  that  it  is  not  a  simple 
compound. 

Chemical  composition.  —  To  show  the  chemical  composition 
of  the  shonkinite  there  is  given  the  analysis  which  has  been 
made  by  Dr.  Hillebrand.  Also  some  analyses  of  these  rocks 
from  other  localities  are  included  and  these  all  show  the 
characteristics  of  the  type  —  rather  low  silica,  low  alumina, 
high  iron,  lime  and  magnesia,  with  moderate  alkalies  and  the 
potash  predominating  over  soda.  In  No.  V.  is  given  the 
average  of  the  first  three  analyses,  and  this  may  be  taken  as 
representing  the  typical  composition  of  shonkinite;  from  it 
all  of  them  vary  but  little.  The  shonkinite  magma  is  that 
which  is  characteristic  of  the  class  of  rocks  which  have  been 
called  lamprophyres.  That  this  magma  exists  in  other  local- 
ities in  a  different  mineralogic,  structural,  and  geologic  form 
is  shown  by  the  comparison  of  the  analyses  given  in  VII 
and  VIII,  the  former  a  thick  intrusive  sheet,  the  latter  of  a 
dike.  The  relation  between  shonkinite  and  absorakite  has 
been  already  noted  by  Iddings.*  In  No.  VI  is  given  for 
comparison  the  analysis  of  a  rock  described  by  Lawsonf 
under  the  name  of  "malignite."  Mineralogically  it  is  closely 
related  to  shonkinite,  in  that  pyroxene  and  orthoclase  are 
the  prominent  constituents;  it  differs  in  the  presence  of 
nephelite  and  in  the  character  of  the  pyroxene  which  is 
segirite-augite,  and  these  differences  are  caused  by  the  larger 
amount  of  alkalies  and  especially  of  soda.  Rosenbusch  J 
places  it  under  the  shonkinites,  including  both  in  the  thera- 
lite  family. 

*  Jour  of  Geol.,  vol.  iii,  p.  953,  1895. 

t  Bull.  Dept,  Geol.  Univ.  Cal.,  vol.  i,  March,  1896,  pp.  337-362. 

t  Mass.  Gesteine,  3d  ed.,  1895-6,  p.  1303. 


454 


PETROGRAPHY  OF  THE 


ANALYSES  OF  SHONKINITES. 


I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

Si02  

48.98 

50.00 

46.73 

50.43 

48.90 

47.85 

50.82 

48.36 

0.813 

A1203  .  .  . 

12.29 

9.87 

10.05 

10.21 

11.07 

13.24 

11.44 

12.42 

0.119 

Fe203  .  .  . 

2.88 

3.46 

3.53  I 

11  57 

3.32 

2.74 

0.25 

5.25 

0.018 

FeO  .  .  .  . 

6.77 

5.01 

8.20  J 

6.33 

2.65 

8.94 

2.48 

0.080 

MgO    .  .  . 

9.19 

8.31 

9.25 

5.58 

9.06 

5.68 

14.01 

9.36 

0.229 

CaO     .  .  . 

9.65 

11.92 

13.22 

14.82 

11.59 

14.36 

8.14 

8.65 

0.173 

Na20  .  .  . 

2.22 

2.41 

1.81 

1.48 

2.15 

3.72 

1.79 

1.46 

0.036 

K20  

4.96 

5.02 

3.76 

3.70 

4.55 

5.25 

3.45 

3.97 

0.052 

H20-110° 
H2O+110° 

0.26 
0.56 

0.17 
1.16 

|    1.24 

087 

1.18 

2.74 

0.58 

5.54 

0.031 

Ti02    .  .  . 

1.44 

0.73 

0.78 

undet. 

0.98 

.  .  . 

0.59 

1.18 

0.017 

P205    .  .  . 

0.98 

0.81 

1.51 

0.70 

1.10 

2.42 

0.20 

0.84 

SO,  . 

002 

C02  .  . 

031 

052 

Cl  

008 

018 

Fl     .... 

0.22 

0  16 

OoOo     . 

trace 

0.11 

0.03 

NiO     .  .  . 

0.07 

MnO  .  .  . 

0.08 

trace 

0.28 

0.19 

0.13 

BaO 

043 

032 

i 

006 

029 

SrO  .  .  . 

008 

007 

i. 

Li20    .  .  . 

trace 

trace 

trace 

99.99 

100.01 

100.54 

99.88 

100.18 

100.65 

100.49 

99.93 

•  .  . 

O  =  C1,F1 

0.08 

0.08 

0.04 

Total 

99.91 

99.93 

100.50 

I.  Shonkinite,  Yogo  Peak,  Montana.     W.  F.  Hillebrand,  anal. 

II.  Shonkinite,  Bearpaw  mountains,  Montana  (Weed  and  Pirs- 
son,  Amer.  Jour.  Sci.,  vol.  I,  1896,  p.  360).     H.  N.  Stokes,  anal. 

III.  Shonkinite,  Square  Butte,  Highwood  mountains,  Montana 
(Weed  and  Pirsson,  Bull.  Geol.  Soc.  Am.,  vol.  6,  p.  414.     1895). 
L.  V.  Pirsson,  anal. 

IV.  Shonkinite,  Monzoni  (Lemberg,  Zeitschr.  d.  deutsch.  Geol. 
GeselL,  1872,  p.  201).     Lemberg,  anal. 

V.  Average  of  I,  II,  and  III. 

VI.  Malignite,  Poohbah  Lake,  Ontario.     (Lawson,  Bull.  Geol. 
Dept.,  University  of  California,  vol.  I,  No.  12,  p.  350).     F.  L. 
Ransome,  anal. 

VII.  "  Lamprophyre."     Between  South  Boulder  and  Antelope 
Creeks,  Montana  (Merrill,  Proc.  U.  S.  Nat.  Museum,  vol.  xvii, 
p.  670,  1895).     L.  G.  Eakins,  anal. 

VIII.  Absorakite  dike,  south  of  Clark's  Fork  river,  Wyoming 
(Iddings,  Jour.  Geol.,  vol.  iii,  p.  938, 1895).     L.  G.  Eakins,  anal. 

IX.  Molecular  proportions  of  No.  I. 


ROCKS   OF  YOGO  PEAK.  455 

Structure  and  classification.  —  The  structure  of  the  Yogo 
Peak  rock  is  purely  hypidiomorphic  granular  and  it  has  all 
the  characteristics  of  a  plutonic  rock.  The  most  striking  and 
dominant  microscopic  feature  is  the  poikilitic  character  of 
the  orthoclase  which  occurs  in  broad  masses,  enveloping  the 
other  minerals,  and  evidently  the  latest  product  of  crystalliza- 
tion. Lawson  *  mentions  it  as  being  also  a  characteristic  of 
malignite. 

From  a  consideration  of  the  molecular  proportions  given 
in  No.  IX.  of  the  table  of  analyses  with  the  results  of  the 
study  of  the  thin  sections  it  is  estimated  that  the  rock  con- 
tains on  the  average  in  percentages  by  weight: 

Pyroxene 35 

Biotite 18 

Olivine 7 

Hornblende,  apatite,  etc.  ...  5 

Anclesine 10 

Soda  orthoclase 25 

100 

This,  of  course,  is  not  accurate,  but  the  control  is  sufficient 
to  make  certain  that  the  variation  cannot  be  more  than  a 
per  cent  or  two  either  way  in  the  more  doubtful  constituents. 
A  mere  inspection  of  the  above  table  shows  that  this  rock 
cannot  be  classed  with  existing  rock  groups,  and  that  its 
erection  into  a  new  group  is  justified.  But  its  occurrence 
in  other  localities  and  the  acceptance  of  the  group  by  other 
petrologists  are  already  matters  of  history  and  render  any 
further  comment  on  this  point  superfluous.!  It  must  be 
stated,  however,  that  the  persistent  appearance  of  quantities 

*  Loc.  cit. 

t  In  his  review  of  the  original  paper  on  Yogo  Peak  by  Mr.  Weed  and  the 
writer,  Neues  Jahrbuch,  1896,  vol.  2,  p.  442,  H.  Behrens  quotes  none  of  the 
analyses,  omits  all  mention  of  the  presence  of  orthoclase  in  the  shonkinite, 
mentions  especially  the  kind  of  plagioclase,  states  with  emphasis  that  it 
resembles  gabbro,  and  thus  produces  a  totally  false  impression  that  only  an 
ordinary  gabbro  had  been  described  and  decorated  with  a  new  name  —  an 
idea  which  any  one  may  see  is  patently  wrong  by  reading  the  original  descrip- 
tion and  observing  the  analysis. 


456  ROCKS  OF  YOGO  PEAK. 

of  biotite  in  all  these  cases,  due  doubtless  to  the  large 
amount  of  MgO  and  K2O  in  the  magma  renders  this  mineral 
a  much  more  constant  feature  of  the  rock  than  was  supposed 
would  be  the  case  when  the  original  specimen  from  Square 
Butte  was  described. 

Shonkinite  at  head  of  Running  Wolf  Creek.  —  This  occur- 
rence has  already  been  mentioned  in  the  description  of  the 
Yogo  Peak  mass.  It  has  also  been  studied  in  thin  section, 
and  excepting  the  fact  that  none  of  it  has  been  seen  to  carry 
any  plagioclase  and  that  the  soda-orthoclase  is  a  little  more 
abundant,  it  so  exactly  resembles  the  type  already  described 
that  no  further  mention  is  necessary. 

SHONKINITE  OF  OTTER  CREEK. 

Besides  the  occurrence  of  shonkinite  at  Yogo  Peak  there 
is  another  in  the  region  of  the  Little  Belt  Mountains  which 
deserves  a  brief  mention.  It  forms  the  large  heavy  mass 
intruded  in  the  upper  carboniferous  beds  on  Little  Otter 
Creek  about  two  miles  or  so  above  its  junction  with  the  main 
Otter  stream.  The  mass  is  exposed  at  least  three  hundred 
feet  above  the  creek,  and  the  outcrops  extend  in  a  long  line 
of  very  columnar  exposures  suggesting  a  sheet  which  must  be 
extremely  thick.  The  road  quarry  at  one  point  has  exposed 
quite  good  fresh  material. 

In  the  hand  specimen  the  rock  is  very  dark  gray  and 
moderately  fine  grained,  the  components  running  from  1 
to  2  mm.  in  diameter.  In  the  section  it  shows  the  same 
minerals  mentioned  above  for  the  Yogo  Peak  shonkinite,  but 
the  amount  of  olivine  which  is  very  fresh  and  has  110  re- 
action rims  is  considerably  greater,  while  biotite  is  much 
less.  The  amount  of  andesine  is  also  less,  only  an  occa- 
sional minute  prism  being  present.  The  orthoclase,  as  usual, 
cements  the  other  minerals.  The  rock,  in  fact,  so  closely 
resembles  the  description  already  given  that  it  needs  no 
further  mention. 


MISSOURITE,   A   NEW  LEUCITE   ROCK   FROM 

THE   HIGHWOOD   MOUNTAINS   OF 

MONTANA. 

BY  WALTER  H.  WEED  AND  LOUIS  V.  PIRSSON.* 
(From  Amer.  Jour.  Sci.  (4)  vol.  2,  pp.  315-323.) 

THE  Highwoods  form  one  of  the  isolated  mountain  groups 
of  central  Montana  which  rise  like  islands  from  the  great 
treeless  plains  stretching  eastward  from  the  slopes  of  the 
Rocky  Mountain  Cordillera,  and  forming  the  great  basin  of 
the  Missouri  River.  They  consist  of  a  group  of  extinct, 
greatly  eroded  volcanoes,  and  the  elevations  which  now  com- 
pose the  area  are  formed  chiefly  of  tuffs,  breccias,  and  lava 
flows  resting  on  Cretaceous  sediments,  together  with  intruded 
stocks  or  cores  of  massive  granular  rocks  which  represent  the 
former  centers  of  volcanic  activity  and  from  which  great 
numbers  of  dikes  radiate  outward  in  all  directions.! 

In  the  preparation  of  a  report  on  the  geology  of  this  moun- 
tain group  it  has  been  found  that  the  body  of  granular  rock 
forming  the  core  at  one  of  the  denuded  volcanic  centers  is 
composed  of  a  new  rock  type  whose  petrologic  character  is  of 
exceptional  interest.  As  the  type,  moreover,  proves  to  be 
of  great  importance  to  systematic  petrography,  it  has  been 
thought  best  to  present  a  brief  account  of  the  rock  and  its 
mode  of  occurrence,  a  more  detailed  description  and  the 
discussion  of  its  geological  and  petrographical  relations  being 
reserved  for  the  report  in  preparation. 

*  Field  geology  and  collection  of  material  by  W.  H.  W. ;  petrography  by 
L.  V.  P. 

t  A  sketch  of  the  geological  features  of  the  region,  with  a  geological 
map,  has  been  published  by  the  authors.  Bull.  Geol.  Soc.  America,  vol.  vi, 
p.  389,  1895. 


458  MISSOURITE,  A   NEW  LEU  CITE 

The  stock  or  core  is  situated  at  the  head  of  Shonkin  Creek, 
a  large  stream  draining  the  northern  part  of  the  mountains. 
The  headwaters  of  this  stream  have  cut  deeply-trenched 
channels  through  the  mountains  and  have  exposed  the  gran- 
ular rock.  The  region,  although  mountainous,  is  almost 
devoid  of  timber.  Smooth  grassy  slopes  with  occasional 
low  rock  exposures  generally  prevail. 

Geological  occurrence.  —  The  new  rock  type  described 
forms  a  stock  of  granular  rock  intrusive  in  Cretaceous  shales 
and  in  the  fragmental  volcanic  material  which  overlies  them, 
both  being  highly  altered  near  the  contact  with  the  igneous 
mass.  These  inclosing  rocks  are  cut  by  a  multitude  of 
dikes,  radiating  from  the  core  as  a  center  and  forming  the 
most  conspicuous  feature  of  the  surrounding  country. 

The  igneous  rock  forming  the  stock  constitutes  an  irregular 
mass  2|-  miles  long  and  in  places  half  as  wide.  Where  cov- 
ered by  the  sedimentary  strata,  the  structure  simulates  that 
of  a  laccolith,  but  careful  study  showed  that  the  intrusion  is 
not  of  this  character.  The  igneous  rock  was  in  part  intruded 
between  the  sedimentary  rocks  and  the  volcanic  breccias 
which  overlaid  them,  and  in  part  injected  along  the  bedding 
planes  of  the  sedimentary  strata  at  the  edges  of  the  stock. 
At  the  south  end  of  the  core  a  coarse  agglomerate  of  massive 
rock  represents  the  filling  of  a  vent  of  a  volcanic  throat,  the 
material  of  the  blocks  and  cement  varying  greatly  in  granu- 
larity but  consisting  essentially  of  the  same  type  composing 
the  main  body  of  the  core. 

Constituting  beyond  all  doubt  a  geological  unit,  the  rock 
mass  of  this  volcanic  stock  varies  considerably  both  in  coarse- 
ness of  grain  and  in  the  proportion  of  its  constituent  minerals. 
The  specimen  selected  for  description  and  analysis  represented 
the  coarsest-grained  and  freshest  variety  observed. 

The  rock  seldom  forms  conspicuous  exposures;  near  the 
contact  it  is  sometimes  weathered  into  castellated  masses  and 
pinnacles,  but  the  usual  outcrop  is  low  and  hidden  by  the 
debris  blocks  into  which  the  rock  ordinarily  weathers.  Platy 
parting  was  observed  near  the  contact,  but  elsewhere  the 
fracture  is  massive  and  determined  by  shrinkage  planes. 


ROCK  FROM  MONTANA.  459 

PETEOGKAPHY. 

Megascopic  characters.  —  Seen  in  the  outcrop,  the  rock 
appears  dark  gray,  coarse  grained,  arid  resembles  many  basic 
massive  rocks  in  appearance.  In  the  specimen  it  is  seen  to 
be  coarsely  and  evenly  granular  and  to  be  composed  of  light 
and  dark  constituents,  the  proportion  by  bulk  being  about 
two  of  the  light  to  three  of  the  dark  minerals.  The  separa- 
tion by  the  heavy  fluids  shows,  however,  that  by  weight  the 
white  mineral  forms  only  one-fifth  to  one-quarter  of  the 
whole.  The  distinction  in  color  is  strongly  marked  and 
gives  the  rock  a  mottled  mosaic-like  appearance. 

Upon  examination  the  dark  constituents  may  be  distin- 
guished as  chiefly  a  greenish  black  augite  in  columnar  masses 
and  aggregates  which  are  never  idiomorphic,  together  with 
an  occasional  speck  of  a  bronzy  brown  biotite  of  ill-defined 
outline  or  a  grain  of  a  deep  yellow  olivine.  Filling  the 
interspaces  between  these  dark  minerals  in  formless  masses 
is  a  very  pale  greenish  gray  substance  which  is  leucite.  The 
average  size  of  crystal  grain  varies  from  2  to  5  mm.,  so  that 
the  rock  is  of  quite  coarse  granular  structure,  and  it  resem- 
bles most  strikingly  in  fact  many  coarse-grained  gabbros. 

Microscopic  characters.  • —  The  thin  section  under  the  micro- 
scope shows  the  minerals  present  to  be  apatite,  iron  ore, 
olivine,  augite,  biotite,  leucite,  and  some  zeolitic  products. 

The  apatite  and  iron  ore,  which  are  present  rather  rarely 
in  moderate-sized  grains,  show  nothing  of  especial  interest 
beyond  that  they  are  found  inclosed  in  the  other  minerals, 
and  the  biotite  frequently  incloses  the  iron  ore. 

The  olivine  is  extremely  fresh,  unaltered  in  any  way,  and 
resembles  the  olivine  of  fresh  gabbros.  It  contains  great 
numbers  of  very  fine  glass  and  iron  ore  inclosures.  It  never 
shows  any  crystal  faces,  but  is  in  rounded,  formless,  anhedral 
grains  which  are  frequently  inclosed  in  biotite  and  augite. 

The  augite  is  of  a  pale  green  color  with  a  tone  of  brown; 
it  is  very  fresh  and  clear,  contains  inclosures  of  ore  and 
specks  of  biotite  and  is  entirely  allotriomorphic,  though  the 


460  MISSOURITE,  A   NEW  LEUCITE 

orientation  of  the  ore  grains  is  at  times  zonal,  thus  indicat- 
ing crystal  planes.  It  has  an  excellent  cleavage  and  twin- 
ning bands  pass  through  it  in  places ;  it  does  not  show  any 
pleochroism. 

The  biotite  is  strongly  pleochroic  between  a  deep  umber 
brown  and  a  pale  yellow  brown ;  it  is  also  entirely  allotrio- 
morphic  though  apt  to  surround  the  other  minerals  in  bands, 
especially  the  olivine  and  iron  ore.  It  is  particularly  char- 
acteristic in  such  cases  that  it  then  passes  from  brown  into 
an  olive  green  variety  which  has  a  mottled,  somewhat 
stringy,  fibrous  appearance.  It  appears  in  these  cases  as  if 
the  brown  variety  had  suffered  from  some  rnagrnatic  process; 
it  does  not  seem  to  be  due  to  any  ordinary  process  of 
weathering. 

Leucite.  —  The  leucite  appears  also  like  the  other  minerals 
in  formless  masses  filling  the  interspaces  between  other  mm~ 
erals.  It  is  perfectly  clear  and  free  from  all  inclusions, 
except  now  and  then  a  grain  of  the  ferromagnesian  minerals. 
Between  crossed  nicols  it  shows  most  beautifully  the  cross- 
banded  twinning  structure  so  characteristic  of  leucite.  It  is 
in  general  perfectly  clear,  limpid  and  fresh,  though  in  some 
areas,  in  delicate  fringes  along  cracks  and  on  the  borders  of 
grains,  a  low  birefraction  shows  that  processes  of  zeolitization 
have  commenced.  This  will  be  described  more  in  detail 
later. 

As  the  presence  of  actual  leucite  itself  has  never  before 
been  demonstrated,  so  far  as  we  know,  in  a  granular  plutonic 
rock,  it  became  a  matter  of  importance  to  prove  its  identifi- 
cation beyond  all  doubt. 

For  this  purpose  a  considerable  portion  of  the  rock  was 
crushed,  sifted,  washed,  and  treated  with  the  potassium 
mercuric  iodide  solution.  Immediately  all  of  the  ferro- 
magnesian minerals  sank,  leaving  the  white  component  float- 
ing. On  then  lowering  the  specific  gravity  by  dilution, 
nothing  except  an  occasional  grain  fell  until  2.465  was 
reached,  when  a  very  little  of  the  white  powder  came  down. 
This  under  the  microscope  proved  to  consist  of  isotropic 


ROCK  FROM  MONTANA.  4G1 

grains  with  attached  particles  of  pyroxene  and  biotite  which 
had  evidently  increased  their  specific  gravity.  This  behavior 
of  the  rock  powder  in  the  heavy  solution  proves  the  absence 
of  all  feldspars  and  nephelite,  thus  confirming  the  micro- 
scopic examination.  On  now  lowering  the  specific  gravity 
of  the  liquid  to  2.405,  the  great  bulk  of  the  white  com- 
ponent came  down,  leaving  a  small  portion  floating.  The 
average  specific  gravity  of  this  material  may  be  taken  as 
2.44.  Examined  under  the  microscope  it  was  found  to  be  a 
very  pure  product,  consisting  of  clear  isotropic  grains  which 
here  and  there  showed  a  faint  birefraction.  An  analysis  of 
it  gave  the  following  results :  — 

Molecular  ratios. 

Si02  54.46  0.907            0.907  =  4.12  =  4 

A1203  22.24  0.216 1                    _     ' 

Fe203  0.68  0.004 ) 

MgO  trace  .  .  .  N 

CaO  0.10  0.0021          ono-w-l 

K20  18.86  0.200  f 

Na20  0.70  0.011  J 

H,0  2.29 


99.33 

The  formula  is  therefore  KAl(SiO3)2  and  the  mineral  is 
consequently  leucite.  There  appears  to  be  a  very  slight 
deficiency  of  alkalies,  and  this  may  be  due  in  part  to  replace- 
ment by  water,  whose  presence  is  undoubtedly  due  to  pro- 
cesses of  zeolitization  which  are  commencing  and  which  may 
be  in  part  the  cause  of  the  faint  birefraction  noticed  above. 
The  small  amount  of  soda  shows  the  leucite  to  be  a  very 
pure  potash  compound.  So  far  as  we  know,  this  is  the  first 
analysis  of  a  leucite  from  other  than  an  Italian  locality,  with 
the  exception  of  that  given  by  Steinecke  *  of  the  mineral 
from  Choi  in  Persia. 

Zeolitization  and  a  probable  new  zeolite.  —  The  small  por- 
tion of  powder  which  was  left  floating  in  the  heavy  solution 

*  Jiingere  Eruptivgesteine  aus  Persien,  Inaug.  diss.,  Halle,  1887,  p.  12. 


462  MISSOURITE,   A   NEW  LEUCITE 

after  the  precipitation  of  the  leucite  at  2.405  was  found  to 
come  down  gradually  as  the  specific  gravity  was  lowered. 
At  2.357  much  had  already  fallen.  At  2.30  a  small  portion 
was  still  floating,  and  this  was  then  thrown  down  and 
analyzed,  in  the  hope  of  learning  what  the  character  of  the 
zeolitization  mentioned  above  had  been.  Examined  under 
the  microscope  it  was  found  to  consist  of  isotropic  grains, 
presumably  analcite,  mingled  with  a  substance  of  low  bire- 
fraction.  The  amount  of  material  was  less  than  0.4  gram, 
and  of  this  TV  gram  was  taken  for  the  determination  of 
water. 

The  analysis  gave  the  following  results :  — 


Ratios. 

A. 

B. 

Si02 
A1203 

50.18 

25.07 

0.836 
0.243 

0.836 
0.243 

4.00 
1.16 

3.46 
1.00 

Fe208 

CaO 

trace 
1.70 

0.030  ) 

K26 

6.53 
8.36 

0.105  V 
0.088  ) 

0.224 

1.06 

0.93 

H20 

9.02 

0.501 

0.501 

2.39 

2.06 

Total       100.86 

The  substance  dissolved  readily  in  acid  with  separation 
of  gelatinous  silica.  The  ordinary  analytical  errors  are  of 
course  somewhat  magnified  by  the  small  quantities  operated 
upon,  but  as  great  care  was  taken  it  is  not  believed  they  are 
sufficient  to  affect  the  ratios.  In  the  first  column  under  A 
one-quarter  of  the  silica  is  taken  as  unity,  under  B  the 
alumina  is  taken  as  unity.  It  will  be  seen  that  the  ratio  of 
the  protoxides  to  the  sesquioxide  to  the  water  is  1  :  1  :  2,  as 
demanded  by  the  analcite  formula,  but  that  there  is  a  defi- 
ciency of  silica.  The  microscope  having  already  shown  that 
two  substances  are  present,  one  of  them  isotropic  and  most 
probably  analcite,  if  we  consider  the  soda  present  as  form- 
ing that  mineral  and  deduct  sufficient  silica,  water  and 
alumina  to  make  with  it  analcite,  the  remainder  reduced  to 
100,  becomes:  — 


ROCK  FROM  MONTANA.  463 

Found.  Ratios.  Calculated- 


Si02 

45.85 

0.764 

0.764 

3.01 

3 

44.6 

A1203 

26.07 

0.253 

0.253 

1.00 

1 

25.6 

CaO 
K20 

3.12 
15.35 

0.056  » 
0.162  j 

0.218 

0.86 

1 

3.4 
17.5 

H20 

9.61 

0.534 

0.534 

2.11 

2 

8.9 

100.00  100.0 

This  yields  approximately  the  formula 
(K2Ca)Al2Si3010.2H20, 

which  is  exactly  that  of  a  natrolite  Na2Al2Si8O10 .  2H2O,  in 
which  potash  and  lime  have  replaced  soda.  The  ratio  of 
CaO  :  K2O  is  1  :  2.91  or  almost  exactly  1  :  3,  and  the  theoret- 
ical composition  of  such  a  compound  (K6CaAl8Si12O40 .  8H2O) 
is  given  above  in  the  column  to  the  right,  and  it  can  be  seen 
that  the  agreement  with  the  amounts  obtained  is  moderately 
close.  If,  on  the  other  hand,  we  assume  that  the  potash 
yielded  by  the  analysis  belongs  to  leucite  and  consider  it  the 
isometric  mineral,  then  the  soda  and  lime  would  belong  to  a 
mesolite-like  mineral,  but  in  that  case  the  agreement  of  the 
ratios  is  very  poor  and  the  water  entirely  too  high.  The 
material  also  floated  at  a  specific  gravity  of  2.30  and  was 
thrown  down  below  this,  which  should  have  excluded  leucite, 
if  present  in  the  proportion  the  amount  of  potash  would 
indicate.  It  is  reasonable  to  suppose  also  that  the  zeolitiza- 
tion  of  leucite  would  yield  a  potassic  compound  and  not  a 
sodium  one.  Taking  into  consideration  the  mathematical 
chances  against  the  improbability  of  the  above  ratios  being 
accidental  and  the  natural  chemical  possibility  of  a  potash 
molecule  similar  to  natrolite,  it  is  not  unreasonable  to  infer 
that  we  have  a  potash  zeolite  of  the  natrolite  type  in  this 
rock. 

In  thin  section  this  zeolite  is  seen  as  small  feathery  par- 
ticles of  low  birefraction  running  in  narrow  bands  around 
the  leucites  and  along  fractures;  it  evidently  attacks  the 
mineral  from  the  outer  surfaces.  In  places  where  it  has 
grown  into  considerable  areas,  the  areas,  while  they  extin- 


464 


MISSOURITE,  A   NEW  LEU  CITE 


guish  as  units,  are  seen  to  be  composed  of  a  curious  grouping 
of  two  substances  in  winding,  interlaced,  vermicular  forms 
almost  exactly  like  micrographic  intergrowths  of  quartz  and 
feldspar,  but  excessively  fine.  Of  these  two  substances  one 
is  birefractive,  the  other  isotropic,  and  from  what  has  already 
been  said  it  seems  probable  that  they  are  a  mixture  of  the 
potash  zeolite  with  analcite. 

Occasional  separate  isotropic  grains  also  occur,  which  do 
not  show  the  cross-banded  twinning  of  the  leucite,  and  these 
are  supposed  to  be  also  of  analcite. 

Chemical  composition.  —  A  mass  analysis  of  the  rock  has 
been  made  for  the  U.  S.  Geological  Survey  laboratory  by 
Mr.  E.  B.  Hurlburt  of  the  Sheffield  Scientific  School,  which 
gave  the  following  results  (average  of  two) : 


I. 

n. 

in. 

IV. 

la. 

Si02 

46.06 

47.28 

46.73 

44.35 

0.767 

A1203 

10.01 

11.56 

10.05 

10.20 

0.097 

Fe203 
FeO 

3.17 
5.61 

3.52 
5.71 

3.53) 

8.20) 

13.50 

0.020 
0.078 

MgO 

14.74 

13.17 

9.25 

12.31 

0.391 

CaO 

10.55 

9.20 

13.22 

11.47 

0.188 

Na20 

1.31 

2.73 

1.81 

3.37 

0.021 

K20 

5.14 

2.17 

3.76 

4.42 

0.054 

H20 

1.44 

2.96 

1.24 

9 

0.080 

Ti02 

0.73 

0.88 

0.78 

? 

0.009 

P205 

0.21 

0.59 

1.51 

? 

.  .  . 

MnO 

trace 

0.13 

0.28 

... 

.  .  • 

BaO 

0.32 

? 

? 

9 

.  .  • 

SrO 

0.20 

? 

? 

? 

.  .  . 

S03 

0.05 

none 

Cl 

0.03 

0.18 

0.18 

.    .    . 

.  .  • 

99.57 

100.08 

100.54 

96.62 

Cl  =  O 

0.01 

0.04 

0.04 

99.56 

100.04 

100.50 

I.  Missourite,  head  of  Shonkin  Creek,  Highwood  mountains, 
Montana.     E.  B.  Hurlburt,  analyst. 

II.  Leucite  absarokite  (Hague,  Amer.  Jour.  Sci.,  vol.  xxxviii, 
p.  43,  1889).     Iddings,  Jour.  Geol.,  vol.  iii,  p.  938,  1895.     J.  E. 
Whitfield,  analyst. 


ROCK  FROM  MONTANA.  465 

III.  Shonkinite,  Square  Butte,    Highwood   mountains   (Bull. 
Geol.  Soc.  Amer.,  vol.  vi,  p.  414,  1895).     (With  corrected  MgO, 
see  p.  424).     L.  V.  Pirsson,  analyst. 

IV.  Leucite  basalt,  Bongsberg  by  Pelm  Eifel  (Hussak,  77  Bd., 
Sitzb.  K.  Akad.  Wiss.  Wien,  I  Abt.,  1878).    E.  Hussak,  analyst. 

la.   Molecular  ratios  of  No.  I. 

This  analysis  brings  out  strongly  the  leading  characteristics 
of  the  rock,  its  very  high  lime,  iron,  and  magnesia,  which 
have  compelled  the  formation  of  such  quantities  of  pyroxene 
and  olivine;  the  predominance  of  potash  over  soda,  which, 
with  the  low  silica,  have  conditioned  the  formation  of  the 
leucite,  and  which  explains  also  why  no  feldspars  have 
formed. 

The  endeavor  to  compare  this  rock  chemically  with  the 
effusive  leucite  basalts,  of  which  it  forms  the  piutoriic  repre- 
sentative, has  not  been  entirely  satisfactory  owing  to  the  lack 
of  accurate  and  complete  analyses  of  them.  A  number  of 
analyses  exist  but  are  deficient  in  important  determinations, 
and  in  some  cases  it  is  clear,  from  what  is  stated  concerning 
the  mineralogical  composition,  that  the  separation  of  the 
magnesia  and  alumina  is  inaccurate,  the  magnesia  being  in 
part  thrown  down  with  the  alumina.  This  is  unfortunately 
an  all  too  common  error  in  rock  analyses.  One  of  the  best 
is  shown  in  the  above  table  in  No.  IV,  and  it  will  be  seen 
that  the  agreement  is  good  in  the  essential  details.  In 
No.  II  is  given  one  of  the  absarokites  of  Iddings,  with  which 
the  missourite,  from  a  chemical  point  of  view,  seems  to  be 
closely  related.  In  No.  Ill  is  shown  the  composition  of  the 
shonkinite  from  the  same  mountain  group.  With  the  same 
amount  of  silica  in  each,  the  lower  alkalies  of  the  shonkinite 
have  permitted  orthoclase  to  form  as  the  dominant  white 
mineral,  while  their  higher  amount  in  the  missourite  has 
produced  leucite  in  its  place.  In  the  shonkinite  the  excess 
of  the  alumina  over  the  alkalies  has  gone  into  the  augite  and 
biotite,  and  the  same  is  undoubtedly  true  in  the  missourite. 
Taking  into  consideration  the  ratios  shown  by  the  analysis, 
the  separations  by  the  heavy  liquid  and  the  study  of  the 

30 


466         A   NEW  LEUCITE  ROCK  FROM  MONTANA. 

section,  the  rock  has  approximately  the  following  mineralog- 
ical  composition :  — 

Iron  ore 5 

Augite 50 

Olivine 15 

Biotite 6 

Leucite 16 

Analcite 4 

Zeolites 4 

100 

Structure.  —  The  structure  is  purely  granitoid,  but  is  not 
hypidiomorphic  since  no  mineral  shows  any  crystal  planes, 
but  all  are  wholly  allotriomorphic.  The  iron  ore,  apatite, 
and  olivine  commenced  forming  before  the  other  minerals, 
but  are  in  rounded  anhedral  grains;  the  augite  and  leucite 
were  crystallizing  contemporaneously,  as  shown  by  the  fact 
that  each  incloses  grains  of  the  other.  In  plain  light  the 
rock  section  appears  precisely  like  those  of  many  coarse- 
grained, massive  gabbros,  and  it  is  not  until  the  nicols  are 
crossed  that  it  is  perceived  that  the  colorless  areas  are  not 
composed  of  striated  plagioclase  but  of  isotropic  leucite. 

Classification.  —  It  is  clear  from  what  has  been  said  in  the 
foregoing  that  this  rock  is  a  new  type,  and  it  fills  a  place 
which  has  hitherto  been  vacant  in  all  systems  of  rock  Classifi- 
cation in  which  either  the  texture,  structure,  and  granularity 
of  rocks  or  their  geological  mode  of  occurrence  is  taken  into 
account.  It  is  the  massive,  granular,  plutonic  representative 
of  the  leucite  basalts  and  bears  the  same  relation  to  them  that 
gabbro  bears  to  the  ordinary  plagioclase  basalts  or  granite  to 
rhyolite.  It  is  closely  related  to  theralite,  shonkinite,  and 
ijolite,  but  cannot  be  classed  under  any  of  these  types  and 
must  therefore  be  distinguished  by  a  special  name  of  its  own. 
We  have  therefore  called  it  missourite  from  the  Missouri 
River,  the  most  prominent  and  best  known  geographical 
object  in  the  region  where  it  occurs. 

WASHINGTON  AND  NEW  HAVEN,  May,  1896. 


ANDESITES  OF  THE  AROOSTOOK  VOLCANIC 
AREA  OF  MAINE. 

BY  HERBERT  E.  GREGORY. 
(From  Amer.  Jour.  Sci.  (4),  vol.  8,  pp.  359-369.) 

ANDESITES  are  rare  rocks  in  the  eastern  United  States,  but 
are  the  most  abundant  extrusives  so  far  found  in  northern 
Maine.  They  form  prominent  hills  and  determine  the  general 
topography  in  some  places,  while  in  others  they  are  repre- 
sented by  isolated  remnants  among  the  sedimentaries.  The 
greater  number  of  occurrences  are  of  lava  and  breccia,  but 
andesitic  ash  and  tuff  are  also  found  well  developed.  In  the 
following  descriptions  only  the  more  important  localities  will 
be  dealt  with  in  detail.  The  andesites  are  located  in  Aroos- 
took  County  in  the  townships  of  Chapman,  Mapleton,  and 
Castle  Hill,  where  they  constitute  prominent  ridges,  known 
as  Edmund's  Hill,  Hobart  Hill,  and  Castle  Hill,  and  several 
less  noticeable  masses. 

FIELD  DESCRIPTION. 

Edmund's  Hill  Andesites.  —  Edmund's  Hill  is  situated  in 
Chapman  township  near  the  middle  of  the  north  township 
line,  and  is  simply  the  highest  part  of  a  ridge  running  N.  -S. 
for  several  miles.  The  hill  itself  rises  some  two  hundred 
feet  above  the  road  at  its  base  and  presents  the  outline  of 
a  drumlin  —  so  evenly  has  it  been  graded  at  each  end.  The 
trees,  brush,  talus,  and  glacial  deposits  entirely  conceal  the 
formations  about  the  base  of  the  hill,  and  it  is  only  after 
climbing  half  the  distance  to  the  top  that  the  bare  rock  is 
found  in  place.  In  climbing  up  the  west  side  of  the  hill 
fragments  of  fossiliferous  sandstone  were  found  amongst  the 
andesite  blocks,  and  about  one  hundred  feet  below  the  top 


468  ANDESITES  OF  THE  AROOSTOOK 

the  sandstone  ledge  outcrops.  The  thickness  and  extent  of 
the  sandstone  could  not  be  determined  accurately  because 
covered  in  so  many  places  with  heavy  blocks  and  small 
fragments  of  the  igneous  rock  fallen  down  from  above.  The 
contact  was  not  seen.  The  entire  top  of  the  hill  is  of  augite- 
andesite.  The  main  mass  is  uniform  in  texture  and  cut  by 
cleavage  cracks  into  large  blocks  which,  when  they  fall  down 
the  slope,  remain  as  huge  masses.  The  south  and  north  ends, 
however,  and  part  of  the  west  side  are  quite  different.  Here 
the  rock  is  split  up  into  long,  thin  slabs  by  a  set  of  parallel 
cracks  remarkably  uniform  in  direction  and  length,  and  they 
retain  their  parallelism  even  when  the  rock  is  folded  or 
faulted.  Cross  cleavages  intersect  these  cracks  every  few 
feet,  so  that  when  the  rock  is  loosened  it  comes  out  in  flat 
slaty  pieces  one-quarter  inch  or  so  in  width  and  several 
inches  or  even  feet  in  area.  The  whole  appearance  is  that 
of  thin-bedded  sedimentaries  which  have  been  folded  and 
faulted.  The  general  direction  of  these  cleavage  planes  is 
N.  30°  E.  on  north  end  and  N.  35  °E.  on  south  end  with  a 
dip  southeast  at  a  high  angle.  The  fault  planes  strike  N.  70° 
E.  and  besides  their  effect  at  the  ends  of  the  hills  in  cutting 
out  the  thin  slabs  they  occur  all  along  the  west  side,  each 
indicating  a  slight  movement.  It  seems  probable  that  the 
Edmund's  Hill  ridge  owes  its  origin  in  part  to  the  formation 
of  a  fault  block. 

The  outlying  knobs  and  hills  to  the  east  of  the  main  mass 
are  also  of  andesite,  usually  microcrystalline,  but  sometimes 
porphyritic.  The  igneous  rock  does  not  extend  far  to  the 
west,  but  is  replaced  by  arenaceous  slates,  and  while  no 
precise  boundaries  of  the  formation  were  determined,  the 
field  relations  suggest  that  the  hill  is  the  remnant  of  a  lava 
flow  over  the  eroded  and  upturned  edges  of  sandy  rocks  of 
Silurian  age.* 

Andesites  of  ffobart  Hill.  —  This  hill  is  an  isolated  mass 
of  andesite  forming  a  prominent  feature  in  the  landscape  as 

*  The  sandstone  at  Edmund's  Hill  contains  an  Eodevonian  fauna  which 
corresponds  closely  with  that  of  the  Gaspe  sandstone. 


VOLCANIC  AREA    OF  MAINE.  469 

one  looks  west  from  Presque  Isle  village.  It  is  situated 
partly  in  Mapleton  and  partly  in  Chapman  townships,  and 
is  surrounded  entirely  by  low,  poorly-drained  swamps  and 
forest  lands,  and  visited  only  for  lumber  and  tan-bark,  which 
are  secured  in  limited  quantities  during  the  winter  season. 
The  hill  is  about  one  and  a  quarter  miles  long  and  three 
quarters  of  a  mile  wide,  and  rises  quite  abruptly  above  the 
plain  to  a  height  of  three  hundred  feet  as  a  single  well  de- 
nned mass  without  branches  or  outlyers.  The  sides  are  every- 
where quite  steep,  and  in  places  present  cliffs  forty  to  fifty 
feet  high.  The  top  is  bare  only  where  fire  has  recently 
destroyed  the  vegetation.  The  talus  slopes  present  a  con- 
fused mass  of  large  and  small  blocks  of  andesite  which 
entirely  conceal  all  outcrops  except  where  cliffs  are  exposed. 
On  the  west  and  north  sides  numerous  boulders  of  red  sand- 
stone and  conglomerate  are  piled  along  the  slope  and  mingled 
with  the  volcanic  material.  These  were  traced  to  their  parent 
ledges  scarcely  a  half-mile  to  the  north,  and  the  boulders 
serve  to  cover  the  contact  of  the  andesite  with  the  Mapleton 
sandstone.*  Specimens  collected  from  various  places  on  the 
hill  show  but  slight  differences  in  composition  and  texture 
except  the  rock  from  the  northwest  corner,  which  is  a  breccia 
of  andesitic  fragments  and  seems  to  be  situated  along  a  fault 
line.  As  was  the  case  with  Edmund's  Hill,  so  here,  no  actual 
contact  between  formations  was  observed,  but  the  sedimen- 
taries  were  traced  to  the  very  base  of  the  hill,  and  the  facts 
indicate  that  the  hill  is  a  remnant  of  a  lava  flow. 

Andesites  of  South  Mapleton. —  In  addition  to  the  prominent 
hills  of  andesite  just  mentioned,  there  are  some  ten  or  twelve 
less  conspicuous  outcrops  in  the  southern  part  of  Mapleton 
township  crossed  by  the  Maple ton-Presque  Isle  road  and 
located  in  the  fields  to  the  north  and  the  south  of  this  road. 
They  occur  usually  as  narrow  ridges,  and  seem  to  be  remnants 
of  lava  flows  which  occupied  former  valleys,  but  are  now  left 

*  The  "Mapleton  sandstone"  here  referred  to  is  a  massive,  and  in  places 
coarse,  red  sandstone,  in  which  plants  (Psilophyton,  etc.)  have  been  found. 
It  is  of  Devonian  age,  but  somewhat  younger  than  the  Chapman  sandstone. 


470  ANDESITES   OF  THE  AROOSTOOK 

standing  because  of  the  erosion  of  the  sedimentaries  on  both 
sides. 

Andesites  of  Castle  Hill.  —  Castle  Hill  is  the  local  name  for 
the  northern  end  of  the  high,  narrow  ridge  extending  N.-S. 
across  the  township  with  the  same  name.  While  not  such  a 
conspicuous  feature  as  Haystack  Mountain  at  the  southern 
end  of  the  same  ridge,  it  forms  the  most  considerable  promi- 
nence on  the  immediate  bank  of  the  Aroostook  River  along 
which  route  all  the  early  travel  lay,  and  hence  was  an  important 
landmark  to  the  first  settlers.  There  is  no  common  local  usage 
as  to  the  limits  of  Castle  Hill,  and  in  this  report  the  term  will 
be  applied  to  the  masses  of  andesite  and  volcanic  elastics  which 
lie  between  the  Aroostook  River  and  the  "  State  Road  "  from 
Ashland  to  Presque  Isle.  It  covers  an  area  2J  miles  long 
varying  in  width  from  J  to  |  mile,  and  is  partly  in  Castle  Hill 
township  and  partly  in  Wade  plantation.  The  wagon  road 
crosses  the  hill  at  its  southern  end,  where  it  rises  little  higher 
than  the  surrounding  plain.  The  eastern  side  has  a  gentle 
slope,  and  is  cut  up  into  several  low  knobs  by  small  streams,  so 
that  the  ridge  effect  is  not  apparent.  The  west  side  is  formed 
by  Welt's  brook  and  the  Aroostook  River,  which  at  this  point 
is  forced  by  it  to  take  the  abrupt  backward  turn  so  noticeable 
on  the  map.  Calcareous  and  arenaceous  slates  are  exposed  in 
the  bed  of  the  river,  while  a  short  distance  back  steep  slopes 
and  cliffs  of  lava  and  ash  rise  to  a  height  of  several  hundred 
feet.  The  hill  is  densely  wooded  and  in  places  swampy,  except 
at  the  southern  end  and  along  the  east  side.  At  these  points 
the  bare  rocks  are  occasionally  exposed  and  present  a  great 
variation  in  character.  In  one  place  heavy  ledges  of  gray  ande- 
site are  exposed,  particularly  on  the  knobs  occupying  the 
northwest  and  southeast  corners  of  Lot  31.  Again  in  the  woods 
east  of  the  mouth  of  Welt's  brook  is  an  outcrop  of  black  silici- 
fied  tuff  between  slates.  On  the  southeast  corner  of  the  hill 
are  loose  ash  beds  containing  fossils,  coarse  and  fine  volcanic 
breccias,  and  pumiceous  lava  in  quite  fresh  condition.  Where 
the  glaciers  have  planed  off  the  old  lavas  and  they  have  been 
protected  from  weathering,  the  outlines  of  bombs  and  pillows 


VOLCANIC  AREA    OF  MAINE.  471 

are  plainly  revealed,  and  when  weathered  these  bombs  are 
loosened  and  drop  out  as  oval  or  egg-shaped  bodies  with  amyg- 
daloidal  surface  and  denser  interior,  and  lie  about  thickly  strew- 
ing the  fields.  In  one  place  there  is  a  cistern-like  depression 
some  ten  feet  deep  and  thirty  feet  in  diameter  made  in  the 
solid  andesite,  while  about  it  are  piled  close  at  hand  a  great 
number  of  very  vesicular  bombs  and  much  glassy  and  brec- 
ciated  ash.  The  whole  appearance  suggests  a  small  blowhole 
made  by  a  single  explosion.  The  striking  fact  about  all  the 
volcanic  accumulations  in  the  Castle  Hill  region  is  their  fresh- 
ness and  their  unmistakable  character. 

PETROGRAPHY. 

Generally  speaking,  the  andesites  of  this  region  belong  to 
well-recognized  varieties  widely  distributed  over  the  earth  and 
differ  in  no  important  particulars  from  the  type  rocks  of  their 
class.  There  are  varieties  found  here,  however,  which  are 
intermediate  between  andesites  and  trachytes  and  also  occur- 
rences with  dacite  facies.  The  exposures  are  numerous  and 
easy  of  access  and  the  specimens  are  no  more  altered  in  compo- 
sition than  if  they  were  Tertiary  lavas  instead  of  Paleozoic. 

Augite-Andesite — Macroscopic  description. — The  largest  and 
best  single  exposure  of  andesite  in  this  region  is  of  this  variety 
and  forms  the  main  mass  of  Edmund's  Hill.  It  does  not  occur 
as  a  solid  compact  mass,  but  is  broken  by  cleavage  and  shear- 
ing planes  into  large  blocks  on  top,  and  into  plates  and  slated 
material  at  the  ends  of  the  hill.  This  slated  and  seemingly 
bedded  appearance,  which  is  so  unusual  in  an  igneous  rock,  is 
the  most  marked  peculiarity  of  the  structure  of  the  hill.  In  a 
few  places  the  rock  is  seen  to  contain  embedded  angular  peb- 
bles of  glass  and  baked  siliceous  material  which  stand  out 
when  it  weathers ;  and  in  other  places  the  rock  presents  a 
banded  surface  of  gray  and  brown,  giving  the  appearance  of 
bedding,  but  which  proves  on  examination  to  be  varying  stages 
of  decomposition  along  potential  cleavages.  With  these  excep- 
tions the  exposed  rock  has  a  uniform  appearance,  gray  where 
weathered,  black  where  fresh. 


472  ANDESITES   OF  THE  AROOSTOOK 

Andesites  are  so  well  known  that  an  extended  macroscopic 
description  is  unnecessary  and  will  not  be  attempted.  The 
hand  specimen  appears  as  a  black,  basaltic-looking  rock,  gener- 
ally dense,  with  a  stringy  effect  and  sprinkled  over  with  glassy 
feldspars  2  mm.  and  less  in  length.  The  weathered  surface  is 
a  layer  of  spongy,  gray-brown  material  in  which  the  pores  are 
made  by  the  decay  of  the  larger  feldspars.  At  the  east  end  of 
the  hill  the  rock  is  much  lighter  in  color,  and  numerous  white 
feldspars  give  it  a  more  porphyritic  appearance. 

Microscopic.  —  As  with  the  hand  specimen,  so  microscopic 
examination  reveals  the  composition  and  structure  expected 
of  a  typical  andesite.  Magnetite,  apatite,  pyroxene,  plagio- 
clase,  and  orthoclase  are  the  original  minerals  present.  The 
plagioclase  crystals  range  in  size  from  laths  2  mm.  In  length 
down  to  the  very  fine  ones  in  the  ground-mass,  but  the  larger 
ones  are  not  abundant  and  do  not  give  the  rock  a  porphyritic 
aspect.  The  plagioclase  forming  the  crystals  outside  the 
ground -mass  was  determined  by  Michel  Levy's  method  to  be 
labradorite ;  but  the  measurements  indicated  two  labradorites 
with  the  formulae:  Ab3An4  and  Ab5An6.  The  larger  feld- 
spars show  strongly  marked  zonal  banding  with  occasionally 
as  many  as  eight  distinct  zones,  which  decrease  in  basicity 
from  the  centre  outward,  but  with  the  original  albite  twin- 
ning running  through  the  whole  series.  This  albite  twinning 
shows  in  nearly  every  feldspar  lath  with  great  distinctness, 
and  twins  on  the  pericline  and  Manebach  laws  also  occur. 
The  Carlsbad  twins  present  are  often  with  one-half  dropped 
much  below  the  other,  and  all  the  twinning  is  more  or  less 
along  irregular  ragged  lines  and  with  unsymmetrical  devel- 
opment. None  of  the  feldspars  are  entirely  fresh,  but  are 
kaolinized  along  the  cleavages  and  zonal  boundaries,  or 
entirely  altered  to  kaolin  and  calcite  except  their  outer 
borders.  They  also  show  irregular  cracks  other  than  cleav- 
age along  which  strain  has  been  relieved.  Glass  inclusions, 
arranged  without  order,  are  numerous  and  stand  out  promi- 
nently in  the  clearer  parts  of  the  feldspars.  Orthoclase  was 
not  found  outside  the  ground-mass  except  as  forming  the  wide 
outer  rim  of  the  zonally -built  plagioclases. 


VOLCANIC  AREA    OF  MAINE.  473 

The  Pyroxenes  are  of  both  monoclinic  and  orthorhombic 
varieties.  The  monoclinic  is  an  augite,  light  colored  in  thin 
section  and  having  an  average  extinction  on  prism  sections 
of  42°.  The  basal  sections  are  quite  fresh  and  show  the 
cleavage  parallel  to  the  prism.  The  pinacoids  are  more 
developed  than  the  prism  faces  and  give  the  appearance  of  a 
square  with  truncated  corners  rather  than  the  more  common 
octagonal  effect.  The  prism  sections  vary  from  stout  forms 
to  those  five  or  six  times  as  long  as  broad.  In  places  many 
small  pieces  are  arranged  in  parallel  position  and  separated 
by  alteration  products  in  such  a  way  as  to  suggest  the  pres- 
ence of  augite  phenocrysts  of  which  these  fragments  are  the 
remnants.  The  orthorhombic  pyroxenes  are  represented  in 
the  darkest  colored  rocks  by  a  few  basal  and  prism  sections, 
but  in  the  gray  varieties  it  constitutes  fully  half  of  the 
pyroxenes  present.  It  is  very  light  colored,  not  at  all  pleo- 
chroic,  and  is  at  times  partly  eaten  away  and  again  occurs 
as  parallel  intergrowths  with  the  augite.  It  seems  to  be  a 
variety  poor  in  iron,  is  optically  +,  and  hence  referred  to 
enstatite.  In  the  fresher  rock  specimens  the  cleavage  cracks 
and  borders  of  the  enstatite  often  show  the  presence  of  a  red- 
brown  fibrous  mineral.  In  the  more  weathered  rocks  this 
mineral  assumes  a  prominent  role.  It  is  here  found  inter- 
grown  with  augite  and  forming  fibrous  laths  with  parallel 
extinction.  Its  pleochroism  is  distinct  with  a  =  light  brown, 
C  —  light  green.  The  presence  of  this  mineral  in  a  slide 
seems  to  be  in  proportion  to  the  absence  of  the  orthorhombic 
pyroxene,  and  this  fact,  together  with  its  shape  and  optical 
properties,  point  to  bastite  and  make  the  supposition  plausible 
that  the  red-brown  mineral  is  the  present  representative  of  the 
original  orthorhombic  pyroxene.  The  magnetite  is  present  in 
grains  or  dust  aggregates,  and  the  apatite  occurs  in  needles, 
laths,  and  rounded  sections  within  the  feldspars. 

The  ground-mass  consists  essentially  of  feldspar  laths,  long, 
narrow,  with  ragged  outline  and  split  ends,  arranged  with 
trachytic  structure  tending  toward  the  hyalopilitic,  and  with 
flow  phenomena  developed  in  places.  No  close  distinction 


474 


ANDESITES   OF  THE  AROOSTOOK 


can  be  drawn  between  the  ground-mass  feldspars  and  those 
which  rise  slightly  above  it,  as  all  sizes  are  represented  grad- 
ing up  to  the  very  largest  ones  present.  Optical  measure- 
ments on  some  of  the  freshest  pieces  in  the  ground-mass 
proved  them  also  to  be  labradorite,  although  orthoclase  must 
also  be  present  as  demanded  by  the  analysis.  Besides  the 
feldspars,  augite  grains  are  scattered  abundantly  throughout, 
and  small  areas  of  brown  glass,  occasionally  with  bubbles, 
also  occur.  The  whole  slide  is  darkened  by  iron  dust,  both 
magnetite  and  limonite  or  gothite.  The  rock  is,  however,  in 
a  remarkably  fresh  state  considering  its  age  and  position,  and 
its  character  is  unmistakable. 


i. 

ii. 

in. 

IV. 

V, 

VI. 

VII. 

Si02  .... 

61.40 

61.58 

61.29 

61.04 

61.45 

61.17 

63.25 

A1203    .  .  . 

16.59 

16.96 

17.68 

15.72 

15.07 

17.74 

14.89 

Fe203    .  .  . 

2.13 

1.75 

6.03 

5.03 

4.46 

1.78 

6.54 

FeO   .... 

3.05 

2.85 

0.30. 

2.15 

1.18 

3.51 

none 

MgO  

2.73 

3.67 

2.45 

3.61 

3.02 

2.76 

0.82 

CaO    .... 

6.17 

6.28 

5.61 

5.34 

5.37 

5.90 

0.59 

Na20  .... 

3.83 

3.94 

4.28 

4.02 

4.00 

3.79 

4.47 

K20    .... 

1.34 

1.28 

1.38 

2.66 

1.22 

1.71 

4.78 

H20-105° 
H20  +  105° 

0.82 
0.88 

0.24) 
1.06) 

0.96 

0.58 

1.23 

0.83 

2.67 

Ti02  .... 

0.79 

0.49 

065 

0.45 

trace 

Zr02  .... 

none 

trace 

none 

VoO* 

0.02 

NiO    .... 

trace 

MnO  .... 

0.13 

trace 

none 

0.12 

BaO   .... 

0.02 

0.03 

.  .  » 

.'  ,  . 

... 

0.06 

.  .  . 

SrO     .... 

trace  ? 

trace 

0.04 

Li2O   .      .  . 

trace 

trace 

0.05 

trace 

P20fi  . 

0.20 

0.22 

trace 

0.14 

0.61 

CO 

none 

078 

Cl    

9 

Fl    ,      ... 

9 

rsoi 

FeS2  .... 

none 

•  .  » 

... 

•  »  . 

3 

•  .  • 

loss 

1  0.29  J 

.  .  . 

0.53 

100.10    99.23   100.63   100.15    100.14    100.00      99.93 


VOLCANIC  AREA    OF  MAINE.  475 

I.  Andesite,  Edmund's  Hill,  Aroostook  Co.,  Maine.    Analysis 
by  W.  F.  Hillebrand. 

II.  Hornblende  andesite,  Mt.  Shasta,  Cal.     Analysis  by  N.  H. 
Stokes,  Bui.  U.  S.  Geol.  Survey,  148,  p.  190. 

III.  Hornblende   dacite,  Anzeiou,  ^Egina.      Analysis  Dr.  A. 
Rohrig,  H.  S.  Washington,  Jour,  of  Geol.,  vol.  iii,  p.  150. 

IV.  Pyroxene  andesite,  Penon   de  Pitayo,   United   States  of 
Columbia.      Kuch :    Geol.   Studien   in   der   Republik   Colombia, 
Pt.  I.     Berlin,  1892. 

V.  Pyroxene  andesite,  Agate  Creek,  Yellowstone  National  Park 
Analysis  by  Whitfield,  U.  S.  Geol.  Survey,  Bui.  148,  p.  134. 

VI.  Hypersthene  andesite,  Crater  Peak  (Lassen  Peak  Region). 
Analysis  by  W.  F.  Hillebrand.     U.  S.  Geol.  Survey,  Bui.  148, 
p.  197. 

VII.  ?  Andesite,  Fox   Islands,   Maine.      Analyses   by  E.  W 
Magruder  and  W.  A.  Jones  in  Johns  Hopkins  University  Lab- 
oratory.    G.  0.  Smith,  Geol.  of  Fox  Islands,  Maine.     Presented 
as  a  thesis,  Johns  Hopkins  University,  1896. 

Analysis.  —  The  analysis  of  this  rock  made  by  Dr.  W.  F. 
Hillebrand  of  the  U.  S.  Geol.  Survey  is  given  in  column  I 
below,  and  with  it  analyses  (columns  II-VI)  of  well-known 
andesites  from  other  localities  are  given  for  comparison. 

From  a  study  of  the  tables  it  becomes  apparent  that  the 
Edmund's  Hill  rock  presents  no  points  of  distinction  from 
recognized  types  found  elsewhere,  and  the  tables  could  be 
greatly  enlarged  by  the  addition  of  closely  similar  analyses. 
The  analysis  in  column  VII  requires  some  notice.  The 
rock  is  described  as  a  red  andesite  with  "  rather  basic  "  feld- 
spars and  with  calcite  and  magnetite  present.  The  altered 
condition  of  the  rock  made  accurate  optical  determination 
impossible.  In  discussing  the  analysis  the  writer  says 
(1.  c.,  p.  34),  "In  its  mineralogical  composition,  this  rock 
approaches  the  basaltic  type,  but,  as  the  analysis  shows,  is 
somewhat  too  acid.  The  olivine  phenocrysts,  moreover,  are 
not  very  numerous  and  there  is  reason  to  regard  this  as 
simply  an  olivine-bearing  phase  of  the  andesite."  The 
description  is  of  an  andesite,  but  there  are  discrepancies 


476  ANDESITES  OF  THE  AROOSTOOK 

between  the  description  and  the  analysis.  No  ferrous  iron  is 
present  to  form  magnetite,  and  if  the  small  amount  of  lime 
forms  calcite,  basic  feldspars  could  not  be  produced.  And 
even  if  the  whole  0.59  per  cent  of  lime  were  present  as 
andesine  or  labradorite  the  amount  is  far  too  small  for  an 
andesite.  According  to  the  generally-accepted  usage  among 
petrographers,  a  rock  with  such  a  high  percentage  of  soda 
and  potash  with  little  lime  and  magnesia  would  be  classed  as 
a  trachyte  or  more  closely,  an  segerine -trachyte. 

Hornblende-andesite.  —  The  largest  single  mass  of  this 
rock  is  Hobart's  Hill,  and  the  freshest  and  most  typical 
specimens  are  from  this  hill  and  from  the  west  bank  of  the 
Presque  Isle  near  the  northwest  foot  of  the  hill,  where 
quarrying  was  attempted  at  one  time.  The  hand  specimen 
shows  a  very  dark  gray,  almost  black,  rock,  fine-grained, 
but  with  a  somewhat  porphyritic  appearance  caused  by  the 
occasional  feldspar  crystals  which  rise  above  the  general 
ground-mass  and  reflect  light  well  from  their  glassy  cleavage 
faces.  Some  few  feldspar  laths  attain  a  length  of  5-6  mm. 
The  rock  breaks  out  into  tabular  blocks  along  the  cleavages 
and  weathers  to  a  brownish  gray  color. 

Microscopic  description.  —  In  thin  section  the  microscope 
reveals  magnetite,  apatite,  titanite,  rarely  a  zircon  lath,  pos- 
sibly augite,  hornblende,  plagioclase,  and  orthoclase  together 
with  considerable  secondary  calcite.  The  feldspars  range 
from  2  mm.  in  length  down  to  minute  microlites.  The 
larger  feldspars  are  commonly  converted  to  calcite,  which 
while  it  indicates  their  basic  character,  also  prevents  their 
accurate  determination.  Those  which  could  be  measured  by 
the  Michel-LeVy  method  proved  to  be  andesine  with  formula 
AbiAni,  hence  more  acid  than  the  feldspars  of  the  augite 
andesine.  They  contain  glass  inclusions,  are  zonally  built 
with  an  occasional  unaltered  outer  border,  and  are  twinned 
according  to  the  Carlsbad  and  albite  laws  but  with  very 
irregular  intergrowths  of  the  parts. 

Hornblende  is  the  only  important  ferro-magnesian  mineral 
present  and  occurs,  like  the  feldspars,  both  as  large  basal 


VOLCANIC  AREA    OF  MAINE.  477 

sections  and  long  laths  often  with  good  crystal  outline  and 
also  as  shreds  in  the  ground-mass.  The  larger  pieces  are 
rarely  in  a  good  state  of  preservation,  but  occur  with  ragged 
edges  and  show  resorption  phenomena.  The  crystal  is  eaten 
into  and  part  of  the  interior  converted  into  magnetite  with  a 
few  augite  grains.  Some  crystals  have  been  almost  entirely 
replaced  by  calcite  and  magnetite,  and  others  are  represented 
by  a  ghostlike  outline  of  magnetite  dust.  Commonly  the 
hornblende  is  now  changed  to  a  green  micaceous  material, 
perhaps  a  variety  of  chlorite,  with  parallel  extinction  and  a 
pleochroism,  c  =  white  green,  a  =  brown  green.  At  times 
the  former  crystal  is  striped  across  with  alternating  bands 
of  green  and  white  in  the  direction  of  the  cleavage  cracks. 
Some  of  the  crystals  classed  as  hornblende  are  so  altered  that 
it  is  impossible  to  say  that  they  may  not  be  augite. 

The  ground-mass  is  formed  of  small,  stringy,  ragged  feld- 
spars and  varies  in  different  slides  from  trachytic  or  pilo- 
taxitic,  with  possibly  a  little  glass,  to  a  type  formerly  quite 
glassy  and  showing  devitrified  areas  with  incipient  micro- 
poikilitic  structure.  The  feldspar  microlites  could  not  be 
accurately  determined,  but  their  average  extinction  indicates 
a  variety  as  acid  as  oligoclase-andesine,  and  if  strict  nomen- 
clature were  to  be  considered,  the  rock  would  be  classed  as  a 
trachyte-andesite. 

Andesites  of  Southern  Mapleton.  —  These  occur  in  several 
localities  and  are  either  identical  with,  or  present  only  minor 
variations  from,  the  Edmund's  Hill  and  Hobart's  Hill 
masses.  The  rock  which  outcrops  in  the  road  two  miles  east 
of  Mapleton  village  has  the  most  glassy  ground-mass  of  all 
the  andesites,  and  its  devitrified  areas  have  the  micropoiki- 
litic  structure  the  best  developed.  Two  outcrops  show  a 
type  much  lighter  in  color  with  much  secondary  and  some 
original  quartz,  giving  the  rock  a  dacite  facies.  The  other 
sections  examined  are  of  the  typical  augite-andesite  or 
hornblende-andesite  of  this  region,  and  require  no  detailed 
description. 

Andesites  of  Castle  Hill  —  Macroscopic  description.  —  The 


478  ANDESITES   OF  THE  AROOSTOOK 

rocks  at  this  place  do  not  have  the  character  of  lavas  which 
have  formed  thick  flows,  but  suggest  rather  the  surface  of  a 
flow  and  are  commonly  arq^gdaloidal,  or  even  slightly  brec- 
ciated  and  ashy,  and  associated  with  them  is  an  abundance 
of  true  volcanic  ash  with  lapilli.  The  rock  exposed  at  the 
southeast  base  of  the  hill  is  striking  in  its  field  appearance. 
Black,  rusty-looking,  spheroidal  or  elliptical  masses  of  lava, 
one  to  two  feet  in  diameter,  first  attract  the  attention  as  they 
lie  loosely  strewn  over  the  surface.  The  solid  ledge  itself  is 
seen  to  be  composed  of  these  forms,  which  have  their  outlines 
well  displayed  by  weathering.  These  sack-like  or  pillow- 
shaped  masses  are  plainly  amygdaloidal  on  the  surface,  but 
usually  much  denser  in  the  interior  and  are  cemented  together 
by  a  coarse  breccia  of  rough  tabular,  spheroidal,  or  irregular 
jagged  fragments  of  glassy  material  and  igneous  rock  of 
similar  composition  to  the  spheres.  In  some  places,  notice- 
ably on  McDonald's  hill  to  the  south  of  Castle  Hill  proper, 
this  structure  assumes  the  form  of  a  conglomerate  of  small 
amygdaloidal  spheres  six  inches  and  less  in  diameter,  closely 
cemented  together  with  angular  pebbles  of  andesite  and  other 
igneous  rocks.  Similar  structures  have  been  described  from 
California,*  and  from  Scotland!  and  elsewhere.  As  noticed 
by  Geikie,  some  basic  lavas,  e.  g.,  the  basalt  at  Acicastello 
in  Sicily,  J  on  flowing  into  water  or  a  watery  silt,  assumes 
a  remarkable  spheroidal  or  pillow-shaped  structure,  "the 
spheroids  being  sometimes  pressed  into  shapes  like  piles  of 
sacks."'  This  may  be  the  explanation  in  the  present  case. 
Another  interpretation  is  that  the  structure  represents  the 
ropy  rolling  surface  at  the  front  of  a  lava  flow.  On  a  fresh 
surface  the  rock  is  dark  bluish-gray,  uniform  in  texture  or 
with  a  rare  feldspar  phenocryst.  While  this  appears  to  be 
the  most  typical  of  the  textures,  it  is  usual  to  find  vesicles 
now  filled  with  calcite  and  fragments  of  volcanic  debris  large 

*  Ransome :  Bull.  Depart.  Geol.  Univ.  of  California,  vol.  i,  p.  106.     Fair- 
banks :  Bull.  Depart.  Geol.  Univ.  Cal.,  vol.  ii,  p.  40. 

t  Geikie :  Ancient  Volcanoes  of  Gt.  Britain,  vol.  i,  p.  193. 
J  Johnston-La  vis  :  South  Italian  Volcanoes,  p.  41. 


VOLCANIC  AREA    OF  MAINE.  479 

enough  to  constitute  a  conspicuous  feature  in  the  hand 
specimen.  In  weathering,  the  amygdaloidal  parts  go  first 
and  leave  the  more  dense  igneous  and  glassy  pebbles  exposed 
as  a  very  rough  surface. 

Microscopic  description.  —  Sections  were  cut  from  the  densest 
material  and  also  from  that  with  macroscopic  inclusions,  and 
when  examined  with  the  microscope  showed  no  difference 
except  in  size  of  vesicular  areas  and  in  method  of  alteration. 
Feldspar  microlites  make  up  the  rock,  parts  of  which  are 
developed  as  areas  of  vesicular  lava.  The  vesicles  range  in 
diameter  from  2  mm.  to  microscopic  dots  and  are  rudely  oval 
in  outline.  The  large  ones  are  merely  the  larger  part  of 
a  rounded  area  of  vesicular  glassy  lava,  containing  a  few 
feldspar  threads  like  the  body  of  the  rock.  Sometimes 
instead  of  one  vesicle,  filled  with  calcite,  the  same  space  will 
be  occupied  by  a  group  of  them,  or  the  concave  inner  border 
of  the  large  one  may  indicate  its  formation  from  several 
smaller  ones.  Some  glassy  oval  areas  occur  with  vesicles 
visible  only  under  the  highest  powers.  All  these  variations 
are  doubtless  caused  by  the  fact  that  different  sections  of 
similar  vesicular  areas  are  exposed  in  the  preparation  of  the 
slide.  The  only  feldspar  phenocryst  seen  in  the  sections  is 
rounded  in  outline,  has  albite  and  pericline  twinning,  and  is 
badly  altered  to  calcite.  Its  extinction-angle  indicates  albite 
or  andesine,  and,  from  the  fact  that  phenocrysts  are  usually 
more  basic  than  the  components  of  the  ground-mass,  is  referred 
to  andesine.  No  ferro-magnesian  mineral  is  present,  but  the 
numerous  patches  of  chlorite  and  the  fact  that  augite  occurs 
in  similar  rock  in  the  immediate  neighborhood  points  to  the 
former  presence  of  pyroxene.  Besides  chlorite,  there  are 
present  as  secondary  products  calcite,  a  few  epidote  grains, 
and  abundant  iron  ore.  One  slide  is  sprinkled  full  of  stringy 
black  iron  ore  in  long  threads  or  lines  of  partly  connected 
dots  which  are  arranged  to  form  barbed  arrows  or  a  network 
of  fibers  which  cross  at  angles  of  60°  and  90°,  thus  imitating 
the  sagenite  structure  of  rutile. 

The  ground-mass  is  of  long,  stringy,  narrow,  frayed  out 


480  ANDESITES   OF  MAINE. 

microlites  of  feldspar  with  trachytic  structure.  Measure- 
ments of  many  laths  gave,  practically,  a  parallel  extinction, 
thus  indicating  oligoclase.  Expansion  structure  is  developed 
where  the  vesicular  areas  are  large  enough  to  affect  the 
orientation  of  the  minute  laths  constituting  the  main  body  of 
the  rock. 

Andesite  Ash  Beds.  —  Beds  of  volcanic  ash  of  an  andesite 
character  are  represented  in  the  region  covered  by  this  paper. 
They  are  particularly  abundant  about  Castle  Hill,  and  will  be 
discussed  in  another  place. 


INDEX. 


ALBANY,  N.  H.,  granite  of,  400. 
Amblygonite,  121. 
Andesite,  467. 

analyses  of,  475. 

augite,  471. 

Castle  Hill,  Me.,  470,  478. 

Edmund's  Hill,  Me.,  467. 

Ground-mass  of,  473. 

Hobart's  Hill,  Me.,  468. 

Hornblende,  475. 

Petrography  of,  471. 

Pyroxene  in,  473. 

Southern  Mapleton,  Me.,  477. 
Argyrodite,  198. 
Aroostook  area,  Me.,  467. 

BANATITE  (Syenite),  Yogo  Peak,  436. 

Bastnasite,  126. 

Bibliography,  Mineralogy,  9. 

Bibliography,  Petrography,  384. 

Bixbyite,  283. 

Borax  Lake,  minerals  from,  261. 

Branchville  Papers,  48. 

CALCITE,  357. 

Campton,  N.  H.,  rocks  at,  394. 

Camptonite,  394. 

analyses  of,  397. 
Canfieldite,  242. 
Childrenite,  124. 
Chrysolite,  388. 
Chondrodite,  218,  221. 
Clinohedrite,  291. 
Clinohumite,  218,  226. 
Contact  rocks,  Albany,  analyses  of,  408. 

of  granite,  Albany,  N.  H.,  400. 
Cymatolite,  98. 

DlCKINSONITE,  61,  117. 

Duraugite,  45. 

EOSPHORITE,  52,  84. 
Eucryptite,  94. 


FAIRFIELDITE,  72,  116. 
Fillowite,  76,  119. 

GAHNITE,  42. 
Ganomalite,  336. 
Gerhardtite,  134. 
Glaucochroite,  330. 
Granite,  Albany,  N.  H.,  400. 
analyses  of,  405. 

HAMLINITE,  287. 

Hancockite,  326. 

Hanksite,  270. 

Hawes,  G.  W.,  bibliography  of,  392. 

Life  of,  391. 
Herderite,  138. 

Highwood  Mts.,  Missourite  in,  457. 
Historical,  Mineralogy,  3. 
Historical,  Petrography,  381. 
Hortonolite,  37. 
Humite,  218,  224. 
Hureaulite,  110. 

IOLITE,  193. 

ABRADORITE,  387,  389. 

rocks,  387.  • 
Leucite  rock,  457. 
Leucophoenicite,  339. 
Jithiophilite,  66,  83. 

tfESOSILICIC  ACID,  338. 

Vlissourite,  457. 

analysis  of,  464. 

leucite  in,  460. 

zeolites  in,  461. 
Mineral    analyses,    interpretation    of, 

348. 
kfonzonite,  440. 

analyses  of,  444. 
>fordenite,  176. 


482 


INDEX. 


NASONITE,  333. 
Natrophilite,  108. 
Northupite,  263. 

OLIVINE,  449. 

analysis  of,  388. 
Ossipyte,  387. 

PEARCEITE,  252. 

Petrographical  Dept.,  History  of,  381, 

Pirssonite,  265. 

Pollucite,  183. 

QUARTZ,  etching  of,  160. 

RALSTONITE,  143. 
Reddingite,  68,  79,  114. 

SHONKINITE,  424,  446,  456. 

analyses  of,  424,  454. 

apatite  in,  417. 

biotite  in,  418. 

olivine  in,  449. 

origin  of  name,  426. 

orthoclase  in,  421,  452. 

plagioclase  in,  421,  452. 

pyroxene  in,  418. 

sodalite  in,  423. 
Spangolite,  168. 


Sperrylite,  151,  157. 

Spodumene,  30,  86. 

Spodumene,  alteration  of,  88. 

Square  Butte,  Mont.,  petrography  of, 

415. 

Staurolite,  207. 
Stereographic  projection,  371. 
Sulphohalite,  343. 
Summaries  of  results,  21. 
Sussexite,  33. 
Syenite,  analyses  of,  397,  429,  438. 

Sodalite  of  Square  Butte,  426. 

of  Togo  Peak,  436. 

THAUMASITE,  246. 
Tiemaunite,  130. 
Topaz,  231. 

Tourmaline,  297,  348,  402. 
Triploidite,  57. 
Turquois,  365. 
Twinning  of  calcite,  357. 
Tysonite,  127. 

WATERVILLE,  N.  H.,  rocks  from,  387. 
Wellsite,  275. 

YOGO  PEAK,  Mont.,  rocks  from,  436. 
ZIRCON  in  granite,  402. 


HQV  2 

OCT  3  1941 


NOV  141941 


*4Y 


**m 


94192 


ill 


